The invention relates to an automatic generator set and grid power supply switching program control device which is high in electromagnetic interference resistance, long-term work stability and switching speed and comprises three phases of power sources a, b and c of a generator set F and three phases of power sources A, B and C for grid power supply G. The power source a of the generator set is connected to one end of a normally closed contact A6 of a grid testing intermediate relay CA after passing a power supply air switch DK2 of the generator set, the other end of the normally closed contact A6 of the grid testing intermediate relay CA is connected with one end of a generator testing intermediate relay CB, the other end of the generator testing intermediate relay CB is connected with the power source c of the generator set, and the other end of the generator testing intermediate relay CB is connected with an end of an auxiliary normally closed contact 1KM<1> of a grid power supply switching alternating-current contactor KM<1>. The automatic generator set and grid power supply switching program control device has the advantages that the automatic generator set and grid power supply switching program control device is simple in structure and low in manufacturing cost, is economical and conforms to national conditions of China.