Abstract: On the background of underwater ammunition attacking the water surface target effectively, a type of variable structure vertical guidance law and control method of underwater ammunition was proposed. By assuming that the target's rolling motion and longitudinal maneuvering were ignored, the movement of target was in a straight line with a constant speed in the horizontal plane and the smart underwater ammunition has no rolling motion, kinematics model equations, dynamic model equations and variable structure vertical guidance law and control of the underwater ammunition were established. Through the application of Matlab/Simulink software, the mathematical simulation system was built and the closed-loop system simulation of variable structure vertical guidance and control of the underwater ammunition was studied. The simulation results show that the proposed design methods of vertical guidance law and control can satisfy the design requirements of vertical attack target, and they are in good agreement with the standard expected.