The invention discloses a trigger circuit. The trigger circuit comprises a channel switching unit, a plurality of level converting units and an output level limiting unit; the channel switching unit is used for inputting level signals into the corresponding level converting units according to the types of photoelectric speed measuring targets, and the output ends of the level converting units areconnected with the input end of the output level limiting unit; and the level limiting unit is used for limiting the voltage magnitude of the level signals passing through the level converting units to be within the set value to be output, and the output signals of the level limiting unit are trigger signals for starting a light weapon end point killing effect testing system. The trigger circuit is suitable for the level signals output by the various different types of photoelectric speed measuring targets, and has the advantages of wide application and high efficiency.