Abstract: ABSTRACT: In order to improve the peak regulation and new energy consumption ability of the power grid, the depth peak regulation carried out by coal-fired power plants has become an inevitable trend. In this study, a 600 MW supercritical once-through boiler that has completed the experiment of 20% deep peak load regulation is taken as an example. Through the replacement of pulverized coal, the balance adjustments of air and pulverized coal, and the analysis of the hydrodynamic stability, the boiler achieves the expected target of peak regulation to 20% of the rated load. And the key points and operating parameters of dry and wet state conversion are introduced in this paper, which provides a reference for the same type boiler of depth peak regulation.