The invention discloses a miniature folding rudder mechanism capable of automatically and repeatedly acting, and relates to the field of size design of air rudders in aircrafts. The miniature foldingrudder mechanism comprises a rotating rudder, a fixed rudder and a miniature folding and unfolding mechanism, wherein the rotating rudder and the fixed rudder are axially butted along an aircraft, theminiature folding and unfolding mechanism is fixedly mounted at the joint of the rotating rudder and the fixed rudder, the rotating rudder driven by the miniature folding and unfolding mechanism rotates by taking the butted line of the rotating rudder and the fixed rudder as an axis and is folded and unfolded, the fixed rudder comprises a pin puller and a lock pin, the pin puller is fixedly arranged at the joint of the fixed rudder and the rotating rudder, and the lock pin is mounted inside the pin puller. When the rotating rudder is folded or unfolded to a set position, the pin puller extends out of the lock pin, the lock pin is inserted into a corresponding hole of the rotating rudder, and the rotating rudder can be locked at the set folding or unfolding position. The miniature foldingrudder mechanism is simple in structure and high in reliability, and the rudder can be automatically unfolded and kept unfolded.