The Party had realized the importance of strengthening ruling legitimacy for a long time,but haven’t solved it very well.After the Cultural Revolution, the Party’s prestige was greatly damaged so,crisis of ruling legitimacy was latent.Deng Xiaoping attached great importance to strengthening ruling legitimacy.He enhanced the persuasive strength of ideology by theory innovation;he increased ruling achievement by developing economics and culture;he demonstrated the ruling party’s value tendency by the party style construction.By these measures, the Party ruling legitimacy remained.Deng Xiaoping’s theory and practice of strengthening ruling legitimacy led to the forming of the “thought of Three Represents” and provided theoretical sources for it.