“Political Marxism” is an important school of contemporary foreign Marxism, which has an important influence in the academic circles of contemporary British and American Marxist studies and forms three generations of academic communities. Focusing on concepts such as social property relations and class analysis, “political Marxism” deeply analyzes the transformation and development of capitalism, and forms a critical theory of “transitional capitalism”. “Political Marxism” has always adhered to Marxs method of historical materialism,and put forward the theory of the agrarian origins of capitalism. It conceives that, first, capitalism arose in the field of agriculture in Britain by chance, and profoundly changed the course of development in Britain and Western European countries. Second, capitalist society presents a process of transformation from agrarian to industrial capitalism, then from industrial to colonial imperialism, and finally from colonial to capitalist imperialism. Third, the ideology of capitalism has become an important part of the capitalist ruling system, forming ideological chains such as “progress”, “democracy”, “unlimited warfare”, and “liberalism”. “Political Marxism” holds that contemporary capitalism has experienced serious crises such as class struggle, economic crisis, ecological crisis and social crisis, and that the overall crisis will inevitably lead to the demise of capitalism. It believes that it is necessary to transcend capitalism and achieve a revival of socialism in the 21st century. The critical theory of “transitional capitalism” of “political Marxism” has very important implications for the development of Marxism in the 21st century, enriching the critical theory of capitalism of contemporary foreign Marxism and promoting the development of socialism with Chinese characteristics in the new era.