A walk-behind, self-propelled machine comprising: a chassis; a handle connected to the chassis; a plurality of wheels for supporting the chassis and being rotatable relative to the chassis; a first motor mounted to the chassis and used for providing a driving force for rotating the plurality of wheels; a working element, movable relative to the chassis to implement the function of the walk-behind, self-propelled machine; and a transmission mechanism connecting the first motor with the plurality of wheels and comprising: a clutch for realizing one-way transmission between the first motor and the plurality of wheels, wherein the clutch has a driving state where the first motor drives the plurality of wheels to rotate and an unlocked state where the plurality of wheels are free to rotate relative to the first motor, and the clutch comprising: a movable member capable of moving between a locked position and an unlocked position; and a driving member which transmits power to the plurality of wheels by means of friction; wherein, when the movable member is in the locked position the clutch is in the driving state where the first motor is capable of driving the plurality of wheels to rotate in a first direction, when the movable member is in the unlocked position, the clutch is in the unlocked state, characterized in that, the walk-behind, self-propelled machine further comprises a second motor for driving the working element to move; wherein when the first motor stops rotating, the plurality of wheels is capable of rotating in a second direction opposite to the first direction and can drive the driving member to move so that the driving member pushes the movable member to move from the locked position to the unlocked position, and when the first motor stops rotating, the plurality of wheels is capable of rotating in the first direction so that the movable member is disengaged from the locked position. a chassis; a handle connected to the chassis; a plurality of wheels for supporting the chassis and being rotatable relative to the chassis; a first motor mounted to the chassis and used for providing a driving force for rotating the plurality of wheels; a working element, movable relative to the chassis to implement the function of the walk-behind, self-propelled machine; and a transmission mechanism connecting the first motor with the plurality of wheels and comprising: a clutch for realizing one-way transmission between the first motor and the plurality of wheels, wherein the clutch has a driving state where the first motor drives the plurality of wheels to rotate and an unlocked state where the plurality of wheels are free to rotate relative to the first motor, and the clutch comprising: a movable member capable of moving between a locked position and an unlocked position; and a driving member which transmits power to the plurality of wheels by means of friction; a movable member capable of moving between a locked position and an unlocked position; and a driving member which transmits power to the plurality of wheels by means of friction; wherein, when the movable member is in the locked position the clutch is in the driving state where the first motor is capable of driving the plurality of wheels to rotate in a first direction, when the movable member is in the unlocked position, the clutch is in the unlocked state, characterized in that, the walk-behind, self-propelled machine further comprises a second motor for driving the working element to move; wherein when the first motor stops rotating, the plurality of wheels is capable of rotating in a second direction opposite to the first direction and can drive the driving member to move so that the driving member pushes the movable member to move from the locked position to the unlocked position, and when the first motor stops rotating, the plurality of wheels is capable of rotating in the first direction so that the movable member is disengaged from the locked position.