How to make a Game object appear 1 sec and disapear 1 sec?

How to make a Game object appear 1 sec and disappear 1 sec? I mean to make a GO flash repeatably.

This question is a bit ambiguous - do you want it to repeatedly appear & disappear (eg, blinking on and off), or disappear permanently after only existing for one second?

If you want to destroy it permenantly, just use the Destroy command with an additional time value (no need for yield & WaitForSeconds):

Destroy(gameObject,1);

The 2nd parameter allows you to specify a time delay for the moment of destruction.

If you want the object to blink on and off at one-second intervals, you should probably enable and disable its renderer component based on the value coming from Time.time, like this:

renderer.enabled = (Time.time % 2 > 1);

Hope one of these solutions helps you!

Do you mean "delete" it by "disappear"?

Just Instantiate it and call a function on your object with

yield return new WaitForSeconds(1);
Destroy(gameObject);

You could use:

renderer.enabled = false

In comination with:

Time.deltaTime