In order to explore the concrete operation and identifcation mechanism of mainstream ideology, discourse practice analysis in the middle-micro level has become a research paradigm worthy of attention.Through the analytical approach of the third generation of discourse theory, and focusing on the empirical perspective of the interaction between state and society in the ideological discourse practice, this article examines hegemonic construction of mainstream ideology in the communication of the movie The Founding of an Army. As a typical ideological discourse practice and in the historical context of post-modern with various identities and subject-object dislocation, the film and its communication has articulated various differential subject positions and signifer elements by creating a "young style" discourse nodal point. Thus, to a great extent, the differential subject positions have been modifed and various identities been integrated, which means the relative success of the identity interpellation and hegemonic construction of the mainstream ideology in the film disseminated to the mass audiences, especially the young generation. This study also shows that the articulation analysis in the third generation of discourse theory has distinctive theoretical explanatory power and methodological feasibility as to facilitating empirical study on mainstream ideology related issues from the perspective of discourse practice, which is worthy of academic exploratory excavation.