When my player pass the Box Collider , i want to "Is Trigger " uncheck, But it still check.. Help me to solve this problem..Here is my Script Screen Shot..

Problems like this are perfect to solve with a Debug.Log();

First questions that you have to ask is: Is that code being run?

I suggest you do these modifications:

Debug.Log("In Trigger function");
if(other.tag == "Player")
     Debug.Log("tag is player");
     other.isTrigger = false;

Now you can see if your code is run.

edit: also i noticed you are setting isTrigger on the “other” object. The other object is the player object. I think you want to disable trigger on the checkpoint object.

getComponent<Collider>().isTrigger = false;

instead of other.isTrigger = false;