As regional security issues have become increasingly severe, the strike capability of individual missiles is gradually failing to meet operational demands, necessitating improved strike efficiency through multi-missile coordination. This paper investigated the control problem of coordinated multi-missile fencing and attack against unknown maneuvering targets and explored the design of the overload ratio, which represents the relationship between missile maneuverability and target maneuverability. Inspired by the self-organizing behavior of biological swarms, this study designed a multi-missile cooperative fencing algorithm using sliding mode control. The algorithm included an attraction term to the target, a repulsion term between adjacent missiles, and a relative velocity convergence term between missiles and the target. The analysis shows that, under this algorithm, the upper bound of the overload ratio can be calculated based on the initial conditions and control parameters, providing technical support for missile formations with a low overload ratio. Numerical simulation results show that the proposed algorithm can effectively achieve multi-missile fencing and attack against unknown maneuvering targets with a low overload ratio. It maintains a safe distance during the fencing phase and rapidly reduces inter-missile spacing during the attack phase by removing the repulsion term to enable coordinated engagement.