The invention discloses a
rocker arm, a valve mechanism and an engine. The
rocker arm comprises a
rocker arm body, a
brake part, a hydraulic gap adjusting device and a control slide valve. A first hydraulic channel, a second hydraulic channel and a mounting cavity are defined by the rocker arm body, and the first hydraulic channel and the second hydraulic channel both communicate with the mounting cavity. The
brake component is movably arranged on the rocker arm main body and is connected with the first hydraulic channel; the hydraulic gap adjusting device is arranged on the rocker arm body and connected with the second hydraulic channel. The control slide valve is movably arranged in the mounting cavity and is provided with a first position and a second position relative to the mounting cavity, the control slide valve at the first position is communicated with the first hydraulic channel and disconnects the second hydraulic channel, and the control slide valve at the second position is communicated with the second hydraulic channel and disconnects the first hydraulic channel. According to the rocker arm, excessive adjustment of the hydraulic gap adjusting mechanism can be avoided under the abnormal control condition.