This paper discusses the labor theory from a new dimension based on the discussion about free time and leisure in Marx’s theory. It holds that free time, as one of the innovation points of Marx’s labor theory, provides space for the existence and development of leisure, that leisure is the unity of individuality and sociality and of mobility and passivity, that free time alienation, labor alienation and leisure alienation have historical homogeneity, and that the realization of free and comprehensive human development is the value orientation of Marx’s leisure theory. Therefore, the rational use of free time is the meaning of Marx’s leisure theory.