diff --git a/src/utils/calUnitTools.js b/src/utils/calUnitTools.js
index 4ad979f..76e348d 100644
--- a/src/utils/calUnitTools.js
+++ b/src/utils/calUnitTools.js
@@ -9,6 +9,13 @@ export function addTj(valueArr, unitArr) {
     mixIndex = thisIndex < mixIndex ? thisIndex : mixIndex
   }
 
+  if (mixIndex === -1) {
+    return {
+      total: 0,
+      unit: 'mL'
+    }
+  }
+
   let total = 0
   for (let i = 0; i < unitArr.length; i++) {
     let thisIndex = unit.indexOf(unitArr[i])