The invention relates to a full-distributed secondary frequency modulation method for a power system microgrid, and belongs to the technical field of power system operation and control. In the method, firstly, the power generation cost functions of a traditional energy distributed power supply and a renewable energy distributed power supply are designed, and the tiny-increasing rates of the traditional energy distributed power supply and the renewable energy distributed power supply are obtained by derivation. A distributed data acquisition and information interaction structure is provided, a subgradient-based consistency algorithm is adopted, and according to data collected by the distributed power supplies and exchanged information, an output power adjustment amount is obtained by iterative computation so as to carry out real-time control of the output power of the distributed power supplies. According to the full-distributed secondary frequency modulation method, power generation cost is guaranteed to be lowest in a secondary frequency modulation process while the frequency realizes quick recovery, and power is reasonably distributed between the distributed power supplies. According to the control method, the frequency oscillation of the microgrid can be avoided, the full-distributed secondary frequency modulation of the microgrid can be realized, and microgrid operation economy is improved.