The utility model provides an electric valve actuator comprising a shell, a motor installed in the shell and a motor rotating shaft connected with a motor, and the motor drives the motor rotating shaft to rotate. The electric valve actuator is characterized in that: the motor rotating shaft is connected with a worm; the shell is further internally provided with a main shaft, the main shaft is provided with a worm wheel and the worm is meshed with the worm wheel; the lower end of the main shaft is connected with a valve rod; when the motor rotates, the motor rotating shaft drives the worm and the worm wheel to rotate so that the main shaft and the valve rod ascends/descends, thus realizing automatic operation; the main shaft is further connected with a linkage device that is combined with a rotary hand wheel; a manual/automatic switching block is installed between the worm wheel and the linkage device and connected with a manual/automatic switching handle; when being switched to manual operation, the manual/automatic switching handle drives the manual/automatic switching block to move so that the worm wheel and the linkage device are separated; and when the rotary hand wheel is manually rotated, the rotary hand wheel drives the main shaft and the valve rod to ascend/descend to realize manual operation.