The work aims to review the research progress of the reactive compatibilization mechanism of PBAT/PLA blend system. Five types of reactive compatibilization mechanisms of PBAT/PLA system were summarized, including catalyzing transesterification reaction, initiating branching and crosslinking reaction, reaction between terminal hydroxyl group and acid anhydride, and reaction between terminal carboxyl group and amino group. The advantages and disadvantages of various reactive compatibilization methods were compared, and the development prospect of reactive compatibilization of PBAT/PLA system was prospected. The compatibility could be effectively improved by multiple reactive compatibilization methods, but the mechanisms of various reactive compatibilization were different. The transesterification catalyst could catalyze the transesterification reaction between PBAT and PLA to generate PBAT-PLA copolyester to achieve the purpose of increasing compatibility. Peroxide could decompose into active free radicals and initiate the formation of PBAT-PLA copolyester. The compatibilizers with dianhydride groups and amino groups could react with the —OH and —COOH respectively to form PBAT-PLA copolyester. These compatibilizers react with terminal groups of polyesters to offset the decrease in molecular weight caused by thermal degradation to a certain extent. The excess compatibilizers with more than two functional groups may cause branching or crosslinking reaction. The reactive compatibilization is also accompanied by uncontrollable reactions, such as thermal aging, hydrolysis, esterification, and transesterification.