Modernization, socialism, and the primary stage are not social conditions in the same historical space and time. But under the historical coincidence, they have formed a interdependent relationship. Socialism established in the historical condition of incomplete modernization can only be socialism in the primary stage, which determines that the overall task of socialism in the primary stage is to achieve socialist modernization. We should use this as a starting point to discuss the historical span and advancement of socialism in the primary stage. In the new era, although the CPC Central Committee has proposed the goal of basically realizing socialist modernization by 2035, it does not mean that historical span of the primary stage of socialism will also be shortened, but will continue to the middle of this century. However, the primary stage of socialism with “special meaning” will be transformed into the primary stage of socialism with “general meaning” after 2035.The realization of socialist modernization by the middle of this century will signify the end of the primary stage of socialism. Then China will enter a new historical orientation, and socialism with Chinese characteristics will also enter a new historical era.