People often make fun of his accent, but he doesn't mind.

make 是动词，意思是"做、制造"，在这里构成短语。 fun 是名词，意思是"乐趣、玩笑"。 of 是介词，表示"关于"或"针对"。 make fun of 是一个固定短语，意思是"取笑、嘲笑某人或某事"。