Abstract: When constructing a new power system, increasing the ratio of new energy output will reduce the system inertia. To ensure the safety and stability of the system frequency, the system inertia needs to be estimated based on the ratio of new energy output to guide the new energy installation planning and the Boot mode arrangement. This paper sorts out the commonly used inertia indicators, and selects the total kinetic energy of the system as the estimated indicator to describe the system inertia. According to the actual specific system and the typical measurement data, the method of inertia estimation after the increase of the new energy output ratio is given. For the large-scale new energy planning system without measurement data, the new energy output ratio is used to infer the start-up capacity of the synchronous machine. Comprehensively considering the synchronous inertia and the virtual inertia, the key parameters and the statistical methods are put forward for the inertia evaluation of the large-scale systems, and an estimation model of system inertia range is established. Finally, based on a provincial power grid, a high-output ratio model of different new energy sources is established, and the relationships between the output ratio, the inertia, and the frequency are analyzed and studied, verifying the validity of the proposed method.