This article examines the dynamics of media centralization and diversification of media in China from 1949 to 2013. Drawing on Bourdieu’s field theory, we conceptualize media structure as the structure of the media field, which encompasses 1) the field boundaries and 2) the internal differentiation of the field. Within the historically changing fields, we also explore 3) the operation of media organizations by using agency theory. We conclude that recent media diversification in China is manifested in the controlled, selective and limited widening of field boundaries; the internal diversification of media structure; and the bifurcation of the contract governing the principal-agent relationship between the party-state and media organizations.