Abstract: In order to quantitatively analyze the reliability level of the power system with UHV penetration, the reliability evaluation model for devices applied in generation and transmission system and UHV AC/DC power transmission system is established by using Monte Carlo simulation method, in which the derating operation state of UHV DC transmission system is considered. Then an overload correction method is presented by combining sensitivity analysis and linear programming, and new reliability indexes that closely relate to UHV are put forward. The example analysis of IEEE RTS-79 system verifies the accuracy of the proposed model. In the end, the model is applied to the actual system of a regional power grid in China, the reliability indices of the system under different scenarios are calculated, and the reliability level of the system with UHV AC/DC transmission system penetration is evaluated, which can provide reference for the operation of the actual system.