The invention relates to a trigger signal control engine decompression device. The device comprises a control chip, a relay, a throttle position switch and a motor, wherein when an engine works, a signal of a trigger and a signal of the throttle position switch are input into the control chip in a balance mode, or when the throttle position switch is turned off, namely in a normal acceleration state, the control chip determines that the engine normally works and does not send any instruction, and the motor stops working; and under the condition that the engine is decelerated, namely when the signal of the trigger is higher than 1,200rpm and the throttle position switch is turned on, the control chip sends a signal to the relay, the relay is operated, the motor pushes a gas inlet valve to move downwards, compressed gas of the engine is completely discharged from the gas inlet valve, and the engine loses compression pressure and stops working, so that the sliding distance of a vehicle is increased, the suction of fuel oil is stopped, a carburetor engine can save oil by over 10 percent, and an obvious effect is achieved.