What should I do if I find that my husband and daughter have an improper relationship?

This kind of thing happens from time to time, but it rarely happens. If the daughter/kloc-is over 0/4 years old and voluntary, even if she wants to take the initiative to do it with her father, it is very difficult. Only you choose to "step aside" and leave her husband. If you make public or report the father and daughter, you may get into trouble, because father and daughter are not good people.