diff --git a/YYText/YYTextView.m b/YYText/YYTextView.m
index 01b1629a..2f3f508b 100644
--- a/YYText/YYTextView.m
+++ b/YYText/YYTextView.m
@@ -1466,11 +1466,13 @@ - (void)_replaceRange:(YYTextRange *)range withText:(NSString *)text notifyToDel
             if (notify) [_inputDelegate selectionDidChange:self];
         }
     }
-    if (notify) [_inputDelegate textWillChange:self];
-    NSRange newRange = NSMakeRange(range.asRange.location, text.length);
-    [_innerText replaceCharactersInRange:range.asRange withString:text];
-    [_innerText yy_removeDiscontinuousAttributesInRange:newRange];
-    if (notify) [_inputDelegate textDidChange:self];
+    if (range.asRange.location+range.asRange.length <= _innerText.length) {
+        if (notify) [_inputDelegate textWillChange:self];
+        NSRange newRange = NSMakeRange(range.asRange.location, text.length);
+        [_innerText replaceCharactersInRange:range.asRange withString:text];
+        [_innerText yy_removeDiscontinuousAttributesInRange:newRange];
+        if (notify) [_inputDelegate textDidChange:self];
+    }
 }
 
 /// Save current typing attributes to the attributes holder.
@@ -3344,11 +3346,15 @@ - (void)setMarkedText:(NSString *)markedText selectedRange:(NSRange)selectedRang
     if (!markedText) markedText = @"";
     if (_markedTextRange == nil) {
         _markedTextRange = [YYTextRange rangeWithRange:NSMakeRange(_selectedTextRange.end.offset, markedText.length)];
-        [_innerText replaceCharactersInRange:NSMakeRange(_selectedTextRange.end.offset, 0) withString:markedText];
+        if (_selectedTextRange.end.offset<=_innerText.length) {
+            [_innerText replaceCharactersInRange:NSMakeRange(_selectedTextRange.end.offset, 0) withString:markedText];
+        }
         _selectedTextRange = [YYTextRange rangeWithRange:NSMakeRange(_selectedTextRange.start.offset + selectedRange.location, selectedRange.length)];
     } else {
         _markedTextRange = [self _correctedTextRange:_markedTextRange];
-        [_innerText replaceCharactersInRange:_markedTextRange.asRange withString:markedText];
+        if (_markedTextRange.asRange.location+_markedTextRange.asRange.length<=_innerText.length) {
+            [_innerText replaceCharactersInRange:_markedTextRange.asRange withString:markedText];
+        }
         _markedTextRange = [YYTextRange rangeWithRange:NSMakeRange(_markedTextRange.start.offset, markedText.length)];
         _selectedTextRange = [YYTextRange rangeWithRange:NSMakeRange(_markedTextRange.start.offset + selectedRange.location, selectedRange.length)];
     }