The invention discloses a preparation method of a p type GaN and AlGaN semiconductor material. A substrate, and a buffer layer or a transition layer, an unintended doped layer and an acceptor doped layer grown on the substrate from bottom to top are contained; in a growth process of the structure, ammonia or nitrogen dimethylhydrazine is used as a five-group nitrogen source; trimethyl gallium or TEGa used as a three-group gallium source, trimethylaluminium or triethyl aluminum used as a three-group aluminium source, and trimethylindium or TEIn used as a three-group indium source are collectively called three-group metal sources; and the trimethylindium or the TEIn is also used as a surface active agent and used in the acceptor doped layer. According to the method, the trimethylindium or the TEIn is used as the surface active agent to assist growth, and simultaneously, the acceptor doped layer is prepared by adopting a delta doping method. According to the method, the doping efficiency of acceptor doped magnesium atoms is increased, and simultaneously, the self-compensation effect is suppressed, so that the p type GaN and AlGaN semiconductor material with favorable crystalline quality and high hole concentration is obtained.