Abstract: In order to identify weak nodes in power grid, a comprehensive weak degree identification method that considers loading rate distribution uniformity of each component of power grid, system loading rate and load loss relative value is given in this paper. Taking IEEE 39-bus system as a simulation example, the results verify the validity of the comprehensive weak degree index in comparison with the existing research methods. In the end, through applying this method to 750kV and 330kV Gansu power grid, the results show that the comprehensive weak degree index can find weak nodes well, which is close to the actual operation characteristics of Gansu power grid. On this basis, the operation and dispatching personnel of the power grid can focus on monitoring weak nodes, and put forward corresponding defensive measures to improve the reliability of the system.