I am very thin and i want to know how to make a perfect and stable body ? whatever i eat, it's just like no effect on my body.why it so ?

Your body: That is just your body. You were just made that way. Some guys were made to be body builders or weight lifters, but your task in life obviously is something else. You must have some other very special talent or ability that will serve the community and world well. So don't worry that you are thin. Just eat a healthy diet and exercise to stay fit so you can use those special talents!