Abstract: With the acceleration of new power system construction and the deepening of power market reform, renewable energy will quickly become the main energy supplier in China and widely participate in the power market, whose volatility and uncertainty may bring about great challenges to the flexibility of the power system. Faced with the obstacle of insufficient peak load regulation resources and the difficulties that the flexibility cost cannot be recovered in the single electricity energy market, this paper proposes a peak load regulation capacity compensation mechanism to stimulate the flexibility transformation of the thermal power, so as to solve the problem of insufficient system flexibility resources in the whole time scale from the medium and long term to the spot. Firstly, the peak load regulation gap of the system is calculated accurately, and the cost model of thermal power deep peak load regulation is constructed. Secondly, the flexible transformation cost of thermal power is divided into the fixed cost and the variable cost. The fixed cost is allocated to the renewable energy with power curtailment, while the variable cost is recovered in the spot market. On the one hand, the reasonable recovery of the necessary flexible cost is guaranteed, and the risks of excessive payment or insufficient recovery are avoided. On the other hand, the deep peak shaving regulation market is included in the electric energy market, which reduces the difficulty of solving the spot market clearing model and clarifying the price signals. Finally, a multi-market mechanism coupling simulation is carried out to verify the effectiveness of the proposed mechanism and model based on an improved IEEE 30-node system.