Folding wing structure is a commonly used form of wing structure for loitering munition, which uses a folding mechanism to fold the wing and automatically unfolds it after the constraint is released. Under the need for miniaturization of the launch unit and transporter, the folding wing model design for the munition is carried out and an optimal path for wing spreading is obtained through analysis. A dynamic model is proposed based on the Lagrange equation and force analysis. Finally, a folding wing expansion mechanism with the motion locking mechanism is designed.