When traveling, how to prevent cotton clothes from wrinkling easily after washing?

Pure cotton? There must be no way. This is determined by the characteristics of the material. And your premise is "when traveling", that is, putting it in a box, there are many things, and it is inevitable to squeeze each other.

It is possible to reduce wrinkles;

The first is smoothness (clothes should be as smooth as possible in the box, and many pieces should be tidied up), and the second is less folding (if you can fold them twice, don't fold them three times).

Third, unique skills (for example, clothes like T-shirts are laid flat first, then rolled up and put in a box, which is absolutely easy to use and definitely not my original work. The key is to roll)

I hope I can help you.