The invention discloses a motion planning method which prevents fore-and-after leaning of a humanoid robot and a device thereof, belonging to the technical field of the motion planning of the humanoid robot. The method comprises: compensation angles are arranged respectively for the rotor angles of an electric motors for the hip joint, the ankle joint and the knee joint of a supporting leg; the corresponding compensation angles are respectively added on the planning angles of the rotor angles of the electric motors for the hip joint, the ankle joint and the knee joint of the supporting leg. The device comprises a compensation angle setting module and an add module, wherein, the compensation angle setting module is used for respectively setting the compensation angle for the rotor angles of the electric motors for the hip joint, the ankle joint and the knee joint of the supporting leg; the add module is used for respectively adding the corresponding compensation angles on the planning angles of the rotor angles of the electric motors for the hip joint, the ankle joint and the knee joint of the supporting leg; wherein, the electric motors for the hip joint, the ankle joint and the knee joint are the electric motors arranged along the left direction and the right direction of the humanoid robot in the axial direction. The invention can effectively reduce the fore-and-after leaning phenomenon when the humanoid robot is supported by a single leg, and improving the landing stability.