Abstract: Multi-energy complementary building energy systems based on flexible load can address the issue of energy supply in isolated rural areas. In this study,the optimization model of isolated multi-energy complementary building energy system is established in Matlab/Simulink. Taking the minimum annual cost of the system as the optimization objective,the genetic algorithm is used to solve the problem. The results show that the annual system cost can be saved by 5.24%,33.11%,and 35.50% respectively when the flexible electric load,the flexible thermal load,and the flexible electrical/thermal load participate in the regulation. After the flexible electrical load participates in the djustrnent,the load shifts to the photovoltaic output period,and the capacity of the energy storage battery and diesel generator is reduced. Compared with the flexible thermal load,the indoor temperature fluctuates more gently when the flexible electrical and thermal load simultaneously participate in the regulation.