The concept of free time is an important part of Marx’s political economy, which was first proposed in his Doctoral Dissertation. With the formation of Marx’s historical materialism, the identification and analysis of the concept of free time runs through Marx’s life-long ideological trajectory, and is finally systematically expounded in "Das Kapital". Free time is generated from the time consumed by surplus labor, and the grasp of free time is the premise of the free development of human beings. However, under capitalist conditions, the free time created by the proletariat is occupied by the bourgeoisie, and the fruits of social progress are therefore stolen by the bourgeoisie. In the constant struggle, the proletariat seems to have "free time", but at the same time, it is caught in the labor of production and consumption, and the information and labor value generated by consuming the surplus labor time are again occupied by capital for free in the form of free time. Prosumers also lose "free time" and fall into labor alienation. Therefore, it is necessary to abandon the alienation of labor, let the workers as a whole regain control of the free time they create, and realize the liberation and free development of all workers.