Compared with Earth, the lunar surface's environment is more complex, which suggests that the nuclear energy Helium–Xenon closed Brayton cycle (NHCBC), supplying electricity to the lunar base, may operate under off-design conditions. A thermodynamic model coupled with the lunar surface environment is established in this paper to analyze the effects of lunar environment exposure, including solar radiation exposure, lunar dust toxicity, and meteorite impact, on a given NHCBC. The results show that the output capacity of a given NHCBC is suppressed during the daytime and enhanced during the nighttime. The lunar dust will improve the system's output capacity at night but will also significantly inhibit the output capacity of the cycle during the daytime, resulting in a fluctuation of 824 % of the system without lunar dust. The output fluctuation of NHCBC is reduced after meteorite impact, while the output capacity of the NHCBC is suppressed, destroyed even worse. The optimization of cycle parameters can alleviate the influence of the lunar environment exposure on NHCBC to a minimal extent. This paper aims to analyze the impact of lunar surface environment exposure on the cycle parameters and output work characteristics of NHCBC and to provide some guidance for the subsequent application of nuclear energy in the lunar base.