You can not be in a relationship where you do not love the guy for fear that you will never find another guy who would treat you like a princess. That is not fair to either of you. What you did by telling him the truth is the best thing. Now YOU need to pull it together and stop leading him on.......
there's a kind man who loves me and cares about me all the time for 3 years but I don't love him back I faced him with that and he refused to go away and I am afriad that I will never find someone like him treat me like princess what I should do?
1 - Stop trying to find a guy who will treat you as a princess. UNLESS you ARE an actual princess. In which case, good luck finding a guy who isn't after you just for a trophy ... Or because your two kingdoms need an arranged marriage.
2 - If he refuses to accept that you will only be friends, you need to break off all ties. Even friendship. Don't hang around him any more. Contrary to what you think, if he can't accept your wishes he really doesn't respect you.
Basic rule of life: You can't maximize everything.
Beyond that comment, I'm not sure what your expectations are for these types of relationships and in particular, what your expectation is and has been for this relationship.
I'd suggest talking to a professional to help you clarify what the best course of actgion for you might be---both now and in the future.