The present invention provides a clutch engaging control method in a hybrid power output device, wherein the device comprises an engine, a first motor, a clutch and a second motor that are connected in sequence, a battery, and a speed reducing mechanism and a drive shaft that are connected to the output end of the second motor; the method comprises: (a) detecting the rotation speed ω2 of the second motor and setting the rotation speed ω2 as the target rotation speed ω0 of the first motor, when the vehicle is driven by the second motor and the engine is required to be started to provide assistance to the second motor; (b) starting the first motor to drive the engine, and controlling the actual rotation speed ω1 of the first motor to be close to the target rotation speed ω0; (c) switching the state of the first motor from a driving motor to a power generator when the actual rotation speed ω1 of the first motor is approximately equal to the target rotation speed ω0; and (d) engaging the clutch. The method can improve the dynamic response time of the engine and suppress impact in the clutch engaging process. The present invention further provides a clutch engaging control system in a hybrid power output device.