The present disclosure provides secondary battery top cover assembly, secondary battery and vehicle. The top cover assembly includes: a top cover plate; an electrode terminal disposed on the top cover plate; an insulating cover; and a short-circuit component including a deformable plate and a conductive plate disposed above the deformable plate, the deformable plate is connected to the top cover plate, and the conductive plate is connected to the electrode terminal. The conductive plate includes a body portion and a protruding portion protruding upwardly from the body portion, and is provided with gas hole, and the protruding portion surrounds the gas hole. The insulating cover includes a covering portion disposed above the conductive plate and covering the protruding portion, a gas flow channel is formed between the protruding portion and the covering portion, and the gas hole communicates with outside of the top cover plate via the gas flow channel.