The p53 protein is an essential tumor suppressor in the human body that plays a critical role in preventing tumor formation by controlling cell cycle arrest and promoting apoptosis. Mutations in the p53 gene are frequently observed in more than 50% of tumor tissues and lead to the generation of mutant p53 proteins, which not only have a dominant-negative effect (DN) that hinders the function of wild-type p53 protein but also have gain-of-function (GOF) effects that stimulate tumor development by regulating cell metabolism, invasion, migration, and other processes. Therefore, mutant p53 protein has become a specific drug target for cancer therapy. However, the lack of a drug-binding pocket and smooth surface of mutant p53 proteins have made them undruggable targets for a long time. In recent years, with the development of high-throughput screening technology and an enhanced understanding of the structure and conformational changes exhibited by mutant p53 proteins, a multitude of small molecule compounds directed against mutant p53 protein have been identified, exhibiting substantial in vitro anti-tumor efficacy. Moreover, some of these compounds have entered clinical trials. This review summarized the direct and indirect strategies for the treatment of cancers targeting mutant p53, with a primary focus on the mechanisms of action of small molecule compounds that reactivate mutant p53 protein or degrade mutant p53 protein. The aim is to provide assistance for the development of innovative drugs targeting mutant p53 protein in the future.