[Objective] To alleviate the difficulties in the consumption of distributed photovoltaic power and peak shaving of the power grid， which have become prominent during the transformation of China's new power system， flexible resources， and a collaborative planning method for transmission and distribution is proposed. [Methods] First， to accurately describe the operational characteristics of transmission and distribution networks and simplify the complexity of the model， refined modeling of substations was achieved at the transmission network layer. In the distribution network layer， the positions of the distribution lines， loads they carry， and distributed photovoltaic systems were treated equivalently. Three types of flexible resources-demand response， distributed energy storage， and load transfer-were integrated in the distribution network layer. First， we ensured the coordinated cooperation between the transmission and distribution grids. Subsequently， load transfer supply constraints and reverse power flow restriction conditions of substations were introduced to meet the supply guarantee and consumption demands under N-1 faults. Finally， concerning the computational difficulty caused by the massive N-1 fault candidate set， the traditional CCG algorithm was improved by adopting the strategies of state evaluation and cut-set packaging， thereby achieving a rapid solution of the model. [Results] The XJTU-ROTS Area C example showed that the new energy consumption rate of the system increased by an average of 4.67%， and the reverse flow risk decreased from 5.45% to 4.86%. [Conclusions] The proposed method can effectively increase the consumption rate of new energy by ensuring a reliable load supply， thereby providing a new concept for the planning of power systems.