When the tactics missile flies across the discrete gust, its dynamic responses and load were investigated. Firstly, the kinematics equations of the missile were put forward, which took into account the influence of structure dynamic on the additional angleofattack of all key section and air helm and the lag effect of the discrete gust on air helm. Secondly, the structure dynamic model of the missile and ‘1cos’ gust model were established, and the formula of dynamic load was given. At last, the dynamic responses and the load of the missile were studied by example.