A continuous firing type trigger structure of a toy gun (air soft gun/BB-gun) includes a valve body disposed behind the output port of a magazine clip in air communication with the gas outlet of a high-pressure gas can, an enclosed socket connected to the rear side of the valve body, a valve tube inserted through the valve body, a spring that pushes the valve tube forwards to keep the air inlet of the valve tube not in communication with the inside space of the valve body, and a piston inserted into the enclosed socket and fixedly connected to a sliding shell on the outside of the toy gun such that the valve tube is moved with the piston forwards (or backwards) to let a high pressure gas be discharged out of the high-pressure gas can into the valve tube to drive an airsoft gun out of the toy gun and to force the piston and the sliding shell backwards after triggering of the trigger of the toy gun, for enabling the piston and the sliding shell to be immediately returned by a return spring for a next firing operation. A hammer is pivoted to the toy gun and releasably secured in place by a spring-supported sear for firing one single airsoft bullet per each hammering action.