diff --git a/packages/mdui/src/components/slider/slider-base-style.less b/packages/mdui/src/components/slider/slider-base-style.less
index 101734a7..821a97e2 100644
--- a/packages/mdui/src/components/slider/slider-base-style.less
+++ b/packages/mdui/src/components/slider/slider-base-style.less
@@ -22,6 +22,7 @@ input[type="range"] {
   cursor: pointer;
   opacity: 0;
   appearance: none;
+  width: calc(100% + 20rem * 2 / @mdui-root-font-size); // for firefox
   .margin(0, -20);
   .padding(0, 12);