Abstract: The theorists of the Second International were not proponents of economic determinism. By distinguishing economic conditions from economic motivations, deconstructing the idealist foundation of economic determinism, and reconstructing the decisive mechanism of the economic base, the theorists of the Second International confirmed the core of the materialist conception of history that "it is ultimately determined by the economy". Its theoretical contribution is reflected in three dimensions: at the epistemological level, it breaks through the shackles of mechanical determinism and establishes the ultimate explanatory power of economic structure; at the ontological level, it constructs an organic holistic view of social forms and reveals the dialectical interaction between economic and non-economic factors; at the methodological level, it develops the complexity principle of historical analysis and emphasizes the mediating characteristics of economic determinism. However, in the process of criticizing economic determinism, the Second International also exposed the deep limitations of the lack of dialectical thinking, simplified historical necessity into economic necessity, and reduced the subject's initiative to a passive executor of economic laws, and finally fell into the theoretical dilemma of linear historical view.