With the continuous growth of electricity demand, the high penetration level of renewable energy has become a trend in the development of distribution networks. However, the large-scale integration of distributed generators (DGs) has results in more prominent problems of power flow, congestion, and voltage fluctuations, which brings challenges to the flexible operation of distribution networks. At the same time, it is necessary to further consider the capacity of lines and the voltage deviation of terminal nodes, so that distribution networks can still retain schedulable space, that is, system flexibility. Therefore, it is necessary to rationally analyze the DG consumption capacity of distribution networks based on their actual operation status. This paper proposes a DG consumption capacity analysis model that considers system flexibility, including evaluation methods for flexibility, improvement of flexibility, and DG consumption analysis model. Through the simulation analysis of the modified IEEE 33-node test system and the construction of several scenarios, the paper verifies the effectiveness of the proposed method and the improvement of power consumption and system flexibility by soft open point.