A reset rocker arm braking method and device are provided. A braking piston hole and an oil drain piston hole which are communicated with a braking oil supply passage are arranged inside a rocker arm, and an oil drain passage is arranged between the braking piston hole and the oil drain piston hole. When the rocker arm is driven by a braking cam lobe of a cam, an exhaust valve is opened to realize braking by a braking piston inside the braking piston hole. When the rocker arm is driven by an exhaust cam lobe of the cam, the rocker arm drives an oil drain piston in the oil drain piston hole to open the oil drain passage to discharge oil, and the lift profile of the exhaust valve is reset and reduced to a conventional exhaust valve lift profile without an engine braking.