Abstract: From the historical development stage of capitalist society, the capital occupies an important position in the development of the society. To a certain extent, capital makes the social productivity get more improved quickly, but at the same time, with the social productivity improving gradually, class conflicts also sharpen, and interest are embodied as a more adversarial form in the class contradictions. Through the analysis of interest thought in Das Kapital, we are enlightened as follows:analyze the interest conflict in wage labor system and contradictory relationship between the poverty gap; analyze the social conflicts of interest under class struggle, and study and realize the current harmony interest relationship; analyze the economic benefit as the social contradictions to interpret the importance of market economy development contradiction and the construction of reasonable distribution system.