To address the challenge of intercepting high-speed maneuvering targets with anti-aircraft missiles,a three-dimensional terminal guidance law that considers the constraints of the terminal line-of-sight angle is proposed.Initially,an adaptive estimation model for target acceleration is established,based on the three-dimensional relative motion model between the missile and its target.This model effectively tracks the line-of-sight angular velocity and achieves high-precision estimation of the target’s maneuver acceleration.Following this,the formula for converting the terminal line-of-sight angle constraints from the ground coordinate to the missile coordinate is derived.Subsequently,a terminal guidance law that is capable of directly utilizing the missile’s seeker measurement information is designed,by integrating sliding mode variable structure control with finite-time convergence theory.It is rigorously proven through mathematical derivations that the proposed guidance law ensures the stability and finite-time convergence of the guidance system’s state variables.Lastly,a digital simulation validation is conducted to evaluate the designed terminal guidance law.The results demonstrate that it not only effectively controls the line-of-sight angle to attain the targeted value but also significantly reduces the missile’s mean miss distance to within 1 meter.Compared to the conventional biased proportional navigation law,it notably decreases the required terminal overload and enhances the missile’s guidance accuracy.Furthermore,by directly incorporating seeker measurement information,the proposed guidance law contributes to simplifying the complexity of the guidance system,offering significant reference and application value for advancing research in air defense missile guidance technology.