Abstract: A rocker arm mechanism of an engine, a system and a method for two-stroke engine brake are provided. The rocker arm mechanism includes a first rocker arm, a second rocker arm and a connection mechanism. One end of the first rocker arm and one end of the second rocker arm is rotatably connected to a shaft, the other end of the first rocker arm is close to a valve of the engine, while the other end of the second rocker arm is close to a cam. The connection mechanism includes a connecting piston and a linkage mechanism. The connecting piston is disposed in the first rocker arm or the second rocker arm, the linkage mechanism is rotatably connected to one end of the connecting piston. The rocker arm mechanism may be used for engine cylinder deactivation and engine brake.