Abstract: The high proportion of renewable energy connected to the power grid makes the uncertainty of the system increasingly prominent, which puts forward higher requirements for the energy supply capacity and response capacity of the system. In order to meet the requirements for high flexibility and high reliability of the system, and fully tap the ability of coupling and complementary coordination among electricity-gas-heat energy sources, an optimal scheduling model of the integrated energy system（IES）considering operation flexibility and energy supply reliability constraints is presented. On the basis of clarifying the concept of flexibility and reliability, the interaction mechanism of improving flexibility and reliability is analyzed. Accordingly, the evaluation indexes of operation flexibility and reliability are deduced, respectively, and the coordination index to demonstrate the interaction influence between them is defined. Based on this, an optimal scheduling model of the IES considering the coordination effect of operation flexibility and energy supply reliability is established by using cost-benefit analysis method and equal response risk method. The nonlinear terms in the model are linearized by incremental linearization, and then directly solved by the mixed-integer linear programming method. Finally, the improved electricity-gas-heat IES 24-20-16 system and electricity-gas-heat IES 118-20-16 system are taken as cases to verify the feasibility of the model and method proposed in this paper.