diff --git a/library/think/db/Builder.php b/library/think/db/Builder.php
index 4ad50fef..c5957848 100644
--- a/library/think/db/Builder.php
+++ b/library/think/db/Builder.php
@@ -116,10 +116,10 @@ abstract class Builder
                         $result[$item] = $val[1];
                         break;
                     case 'inc':
-                        $result[$item] = $this->parseKey($val[1]) . '+' . $val[2];
+                        $result[$item] = $this->parseKey($val[1]) . '+' . floatval($val[2]);
                         break;
                     case 'dec':
-                        $result[$item] = $this->parseKey($val[1]) . '-' . $val[2];
+                        $result[$item] = $this->parseKey($val[1]) . '-' . floatval($val[2]);
                         break;
                 }
             } elseif (is_scalar($val)) {