The invention relates to a seat and a protection device. The protection device comprises a left pressing plate, a left rotating shaft, a left ratchet wheel, a left pawl, a left unlocking device, a right pressing plate, a right rotating shaft, a right ratchet wheel, a right pawl and a right unlocking device; the left pressing plate is fixed to the left rotating shaft, the left ratchet wheel is arranged at one end of the left rotating shaft, and the left unlocking device is fixedly connected with the left pawl and controls the left pawl to move to lock or unlock the left ratchet wheel; the rightpressing plate is fixed to the right rotating shaft, the right ratchet wheel is arranged at one end of the right rotating shaft, the right unlocking device is fixedly connected to the right pawl andcontrols the right pawl to move to lock or unlock the right ratchet wheel, a one-way bearing is arranged between the left rotating shaft and the left ratchet wheel, and a one-way bearing is arranged between the right rotating shaft and the right ratchet wheel. After the left pressing plate and the right pressing plate are combined, a heart-shaped space is formed, the space conforms to the shape ofthe abdomen of a human body, the waist holding type protection effect is achieved, the safety is high, the degree of freedom of the upper part of the body and the legs of a passenger is high, ridingis more comfortable, and the device is specially suitable for row seat application.