To make a crochet rug like this first you have to prepare t-shirt yarn. For that cut all the t-shirts available to you in strips. Join every two strips by interlocking them in the way shown. Prepare long strips of yarn like this and roll them into balls. Then with the help of a large crochet hook start crocheting the rug. If you like you can first work with one color and then change the colors as you make the rug bigger and bigger.
So either make a rainbow rug or create it from a single color it will look absolutely wonderful. If you require more details visit craft stylish. Happy crocheting!