How can I make my parents approve of my boyfriend?

Why don't they approve of him? Ask your parents why. It won't hurt. It may be hard, though, but I'm sure you want to know why. I'm sure your parents care for you, and want what's best for you. There is a really good chance that they know more than you of what is best in a relationship because they more than likely experienced those. If you don't think your parents really know your boyfriend, then ask. Don't judge, yet. Try to see it from their view. If they are right, then make your decision if you should stay with him or not. If they are assuming too much too quickly, then relax. It takes time.