Abstract: With the large-scale access of new energy to the power grid, it will bring great challenges to the power grid system with coal-fired thermal power units as the main power structure. Due to the randomness and intermittency of the power generation output of new energy, the difficulty of peak load regulation of the power grid system increases, affecting the safety and stability of power grid operation. In the current situation that thermal power units are generally faced with flexible deep peak shaving, an adaptive undisturbed switching control strategy based on the original DCS system of the unit is proposed, which is suitable for the normal operation condition and deep peak shaving operation condition of the unit. The implementation process only needs logic configuration, without software and hardware changes. The application and practice show that it has the characteristics of strong operability, low investment, high safety factor and good effect, It has great reference significance for similar projects of similar units.