Abstract: With the rapid development of UHV power grid construction in China, the coupling relationship between AC and DC is becoming more and more complex, the stability support requirements of DC drop point are high, and the development of source-grid-load is not synchronized, In order to optimize the ability of resource distributing and improve the level of power supply, this paper proposes a method for evaluating the maximum power supply capacity of Ultra-high voltage power grid considering section coupling and DC stability support. Firstly, considering the maximum power supply capacity of the power grid, a certain section margin and reserve are evenly distributed in the whole power grid when the maximum power supply capacity is reached. The three objective functions of the maximum power supply, the maximum minimum section margin and the most balanced reserve are selected. The reserve capacity constraint, non-section coupling constraint and section coupling constraint are used as constraints to establish the maximum power supply capacity evaluation model of the ultra-high voltage power grid. The model is solved by the normalized normal constraints method, and then technique for order preference by similarity to ideal solution is used to select solution and complete the maximum power supply capacity evaluation. Based on the data of a province, this paper carries out an example analysis to illustrate the effectiveness of the proposed method.