Failing to promptly close the valve whose circuits have been burnt out is one of the important causes leading to an amount of oil leakage after the Dalian oil pipeline explosion. Moreover, the opening/closing torque of the manual valves will be bigger due to no actions for a long time, corrosion, rust, etc. And the operators will stay in a dangerous environment for a long time and thus they will have life problems when there are abnormal conditions or accident conditions. This paper proposes a design idea of a novel rapidly-opening/closing actuator of a manual valve, in order to resolve the problem that how to open/close a manual valve rapidly. The research on the rapidly-opening/closing actuator of a manual valve should include the calculation of the opening/closing torque of the manual valve and the designs of the deceleration machine and the chuck. The output shaft of the deceleration machine connects with a chuck, while the chuck connects with the wheel of the valve. The work principle of the actuator is that a motor drives the rotation movement of the deceleration machine so as to realize the rapid opening/ closing of the valve. This paper mainly focuses on the design of the deceleration machine, wherein the structure of planetary gear is designed through the theoretical calculation and the computer-aided design method. The research of the method provides the design method and the technical support for the design of the rapidly-opening/closing actuator of the manual valve. The actuator could be employed to the safety prevention departments of the chemical industries after the successful design of the device. The device can be utilized to cope with the problem that how to open/close a manual valve with more rotating laps or in emergency conditions rapidly. Moreover, the accident rescue ability of the chemical industries will be further improved, and the loss of the accidents will be reduced.