Abstract: Primary frequency control refers towhen the frequency of the power grid deviates from the rated value,the control system of units in power grid and theactive power increase and decrease of active powerunitslimit the frequency change and maintain the stability of the power grid frequency. The primary frequency control loop is generally divided into CCS primary frequency modulation loop and DEH primary frequency modulation loop. These two parts of the frequency modulation loop work together,in which DEH primary frequency control acts quickly,and CCS primary frequency control final stable load. The primary frequency control function of the optimized unit makes the DEH primary frequency control action directly controling the steam turbine regulating valve to change the load of the unit,which is the demand of the unit to quickly respond to the primary frequency control. The CCS primary frequency control final stable load is equivalent to adjusting the set value of the load after the primary frequency control action,and ensures that the action direction is the same as that of DEH. The final stable load reaches the required value. It promotes the assessment data to meet the requirements of network adjustment,improves the network related service ability of the unit,and reducesthe amount of assessment deduction.