Demand side management can improve energy efficiency and reduce the maximum load demand, which is equivalent to an indirect increase in power generation capacity of the system, thus can improve the reliability of generation system. The reliability indexes of generation system is introduced briefly, the reliability analysis models including generation capacity model and load model are built for generation system, and the non-sequential Monte Carlo method applied in generation system reliability evaluation is analyzed. The IEEE Reliability Testing System (RTS) is set as an example to make a quantitative analysis of the influence of demand side management on generation system reliability evaluation. The analysis results show that implementation of demand side management can improve the energy utilization and reliability of generation system, thus the system can be more secure, economic and reliable to supply electric power for electricity users.