Abstract: Under the goal of "double carbon", China's power system urgently needs deep decarbonizing transformation, and the traditional coal-based power energy structure will undergo a fundamental transformation. It is an important subject for the construction of new power system to study the orderly withdrawal of thermal power units and realize safe and economic low-carbon transformation. To this end, this paper proposes a multi-phase planning method of source- network-storage coordination considering the orderly retirement of thermal power, which can improve the economic benefits of low-carbon transformation of power system based on ensuring the construction of green and safe new power system. First, a multi-stage planning model of source network storage cooperation is established, considering the decommissioning of thermal power units. Then, the model linearization and solution acceleration methods are designed to improve the operation efficiency of the model. Finally, taking the HRP-38 test system as a typical example, the paper proposes the thermal power development and retirement path under the joint influence of the carbon emission quota and the gradual increase of the proportion of new energy, and evaluates the effectiveness of the multi-stage planning model including the orderly retirement of thermal power units from the perspective of inertia demand.