diff --git a/cotk/metric/metric.py b/cotk/metric/metric.py
index 10d7ccfd..f8e929af 100644
--- a/cotk/metric/metric.py
+++ b/cotk/metric/metric.py
@@ -463,7 +463,7 @@ def run_f(self, ele):
 		'''Auxiliary function which returns:
 			* **sentence-self-bleu**: sentence-self-bleu value.
 		'''
-		return sentence_bleu(ele[0], ele[1], ele[2], smoothing_function=SmoothingFunction().method1)
+		return sentence_bleu(ele[0], ele[1], smoothing_function=SmoothingFunction().method1)
 
 	def close(self):
 		'''Return a dict which contains:
@@ -476,21 +476,17 @@ def close(self):
 		ref = self.hyps[:self.sample]
 
 		try:
-			result = {}
-			for ngram in range(2, 5):
-				weight = tuple((1. / ngram for _ in range(ngram)))
-				if self.sample >= 1000:
-					pool = Pool(multiprocessing.cpu_count())
-					bleu_irl = pool.map(self.run_f, [(ref[:i]+ref[i+1:self.sample], ref[i], weight) \
-										for i in range(self.sample)])
-					pool.close()
-					pool.join()
-				else:
-					bleu_irl = []
-					for i in range(self.sample):
-						bleu_irl.append(self.run_f((ref[:i]+ref[i+1:], ref[i], weight)))
-				result["self-bleu-%d"%ngram] = 1.0 * sum(bleu_irl) / len(bleu_irl)
-			return result
+			bleu_irl = []
+			if self.sample >= 1000:
+				pool = Pool(multiprocessing.cpu_count())
+				bleu_irl = pool.map(self.run_f, [(ref[:i]+ref[i+1:self.sample], ref[i]) \
+									for i in range(self.sample)])
+				pool.close()
+				pool.join()
+			elif self.sample > 1:
+				for i in range(self.sample):
+					bleu_irl.append(self.run_f((ref[:i]+ref[i+1:], ref[i])))
+			return {"self-bleu" : 1.0 * sum(bleu_irl) / len(bleu_irl)}
 		except ZeroDivisionError as _:
 			raise ZeroDivisionError("Bleu smoothing divided by zero. This is a known bug of corpus_bleu, \
 				usually caused when there is only one sample and the sample length is 1.")
diff --git a/tests/metric/test_metric.py b/tests/metric/test_metric.py
index 0408bb10..cc00ed3b 100644
--- a/tests/metric/test_metric.py
+++ b/tests/metric/test_metric.py
@@ -7,7 +7,7 @@
 
 from cotk.metric import MetricBase, \
 	BleuPrecisionRecallMetric, EmbSimilarityPrecisionRecallMetric, \
-	PerplexityMetric, MultiTurnPerplexityMetric, BleuCorpusMetric, MultiTurnBleuCorpusMetric, \
+	PerplexityMetric, MultiTurnPerplexityMetric, BleuCorpusMetric, SelfBleuCorpusMetric, MultiTurnBleuCorpusMetric, \
 	SingleTurnDialogRecorder, MultiTurnDialogRecorder, LanguageGenerationRecorder, HashValueRecorder, \
 	MetricChain
 from nltk.translate.bleu_score import corpus_bleu, sentence_bleu, SmoothingFunction
@@ -671,6 +671,66 @@ def test_bleu_bug(self):
 			bcm.forward(data)
 			bcm.close()
 
+self_bleu_test_parameter = generate_testcase(\
+	(zip(test_argument), "add"),
+	(zip(test_shape, test_type), "multi"),
+	(zip(test_gen_len), "multi"),
+)
+
+
+class TestSelfBleuCorpusMetric:
+	def run_f(self, ele):
+		'''Auxiliary function which returns:
+			* **sentence-self-bleu**: sentence-self-bleu value.
+		'''
+		return sentence_bleu(ele[0], ele[1], smoothing_function=SmoothingFunction().method1)
+
+	def get_self_bleu(self, dataloader, input, gen_key):
+		gens = []
+		for gen_sen in input[gen_key]:
+			gen_sen_processed = dataloader.trim_index(gen_sen)
+			gens.append(gen_sen_processed)
+		refs = copy.deepcopy(gens)
+		bleu_irl = []
+		for i in range(len(gens)):
+			bleu_irl.append(self.run_f((refs[:i]+refs[i+1:], refs[i])))
+		return 1.0 * sum(bleu_irl) / len(bleu_irl)
+
+	@pytest.mark.parametrize('argument, shape, type, gen_len', self_bleu_test_parameter)
+	def test_close(self, argument, shape, type, gen_len):
+		# 'default' or 'custom'
+		# 'pad' or 'jag'
+		# 'list' or 'array'
+		# 'equal' or 'unequal'
+		# 'random', 'non-empty', 'empty'
+		# 'random', 'non-empty', 'empty'
+		dataloader = FakeDataLoader()
+		gen_key = 'gen' \
+			if argument == 'default' else 'gk'
+		data = dataloader.get_data(gen_key=gen_key, \
+								   to_list=(type == 'list'), \
+								   pad=(shape == 'pad'), \
+								   gen_len=gen_len)
+		_data = copy.deepcopy(data)
+		if argument == 'default':
+			bcm = SelfBleuCorpusMetric(dataloader)
+		else:
+			bcm = SelfBleuCorpusMetric(dataloader, gen_key)
+
+		bcm.forward(data)
+		assert np.isclose(bcm.close()['self-bleu'], self.get_self_bleu(dataloader, data, gen_key))
+		assert same_dict(data, _data)
+
+	def test_self_bleu_bug(self):
+		dataloader = FakeDataLoader()
+		gen = [[1]]
+		data = {'gen': gen}
+		bcm = SelfBleuCorpusMetric(dataloader)
+
+		with pytest.raises(ZeroDivisionError):
+			bcm.forward(data)
+			bcm.close()
+
 multi_bleu_test_parameter = generate_testcase(\
 	(zip(test_argument), "add"),
 	(zip(test_shape, test_type), "multi"),