Abstract: Purity is vital to the survival and development of our Party,through which the mass people get to know the charm and practical power of Marxism ideology.Purity of our Party can reinforce and strengthen the guiding position of Marxism ideology,thus it is a key dimension to construct social identity of mainstream ideology and it is important to maintain the inner unity of the two.Presently,the loss and declination of our Party’s purity has weakened the mass people’s faith in the party,bringing great challenge to the construction of social identity of mainstream ideology.It is the essential requirement and an inevitable choice to probe into the mechanism and the way to maintain the purity of our Party in constructing social identity of mainstream ideology.

Key words: party purity, social identity of mainstream ideology