How long have you been dating for? If he says anything negative, maybe emphasise why your boyfriend makes you so happy, how much he cares for you etc. Parents worry mainly because they want their daughter with someone who makes them happy and not break their heart. Your father is worried that this guy is using you when in fact he is not. You need to communicate this to him. Of course
you know this guy well so it's no problem to you, but your father does not know him and so can only think of him in stereotypical terms. Is it a possibility that your dad could meet your boyfriend even just casually to give him an idea that he's not a horrible person? The more he gets to know about him (in a good way) the more likely he will be able to understand and hopefully respect the relationship. Good luck