The utility model discloses a phase tracking and triggering control device of a vacuum trigger switch under alternating current condition, wherein the device mainly comprises a voltage transformer, a signal conditioning unit, a signal collecting unit, a data processing unit, a triggering control unit, a state monitoring unit and a triggering unit; the primary side of the voltage transformer is connected on the main electrode alternating current input end of the vacuum trigger switch, and the secondary side of the voltage transformer is connected with the input end of the signal conditioning unit; the output end of the signal conditioning unit is connected with the input end of the data processing unit through the signal collecting unit; the output end of the signal collecting unit is connected with the triggering control unit; the output end of the triggering control unit is connected on the input end of the triggering unit; the input end of the state monitoring unit is connected with the triggering unit and the vacuum trigger switch, and the output end of the state monitoring unit is connected with the data processing unit; and the output end of the triggering unit is connected on the triggering electrode of the vacuum trigger switch. The phase tracking and triggering control device disclosed by the utility model can be used for accurately controlling the trigger of a triggering source of the vacuum trigger switch in a repeated frequency pulse power system.