In recent years, peak load has been growing yearly and peak-valley difference of load has been increasing, which brings great pressure on grid operation. Two typical thermostatic controlled loads (TCLs) ie, water heater and air conditioning are selected as controlled objects. The phenomenon of payback effect is taken into consideration and a linear planning mathematical model of load regulation is put forward to maximize the amount of peak load reduction orderly through full-time and split-time control strategies. Through the load regulation of typical summer day in Nanjing, the amount of peak load reduction under different conditions are analyzed. The results verify the validity of the proposed linear planning mathematical model.