Hi ,i am 20 years old and my height is 5'7 and i am doing workout for abs will this exercise affect my height. if yes then what exercise will be better for my height?

Ab exercises: Doing abdominal exercises should not effect your height in any way. If you strengthen your core- you may stand straighter which could give appearance of being a little bit taller.

Basics: At age 20 you are as tall as you will ever be, To the extent exercise helps you maintain a good posture, you will maintain that appearance easier. No exercise, stretch, hanging upside down, diet or other endeavor will increase your height beyond where it is now.