A dual UHVDC is fed into the same grid, and there is strong coupling between the channels. It is necessary to develop a suitable maintenance evaluation method for the key section of the power receiving terminal. In order to do this, a maintenance evaluation method based on safety risk probability for the key section channel of double UHVDC feed in a grid is proposed. First, a grid strength evaluation method is established based on the analysis of the strength evaluation index of the grid receiving terminal. The coupling strength of the grid structure is evaluated by short circuit ratio. From the results of the evaluation and considering the safety factors of critical section channel maintenance, a quantitative assessment method of safety risk for UHVDC critical section maintenance is proposed. A fuzzy evaluation model of safety risk is constructed, and the reliability of the whole grid during the maintenance of the key section of UHVDC channel is evaluated quantitatively according to the change rate of each index. Finally, simulation and evaluation are carried out on the grid structure composed of Qing-Yu UHVDC and Tian-Zhong UHVDC in a provincial power grid, and the effectiveness of the proposed maintenance evaluation method is verified. Dangerous maintenance scenarios are identified by the proposed method and have gained the attention of the grid operation department and are forbidden in actual operation. This work is supported by the National Key Research and Development Program of China (No. 2018YFB0905200) and the Project of State Grid Henan Electric Power Company (No. 52170219000M).