MEMS inertial measurement units are commonly used in short-range and terminal phase of tactical missiles. Due to their accuracy constraints, the inertial navigation resolving error of the missile cannot be neglected, it may have a significant impact on the guidance mode switching of a compound guidance system of missile in flight. In order to realize effective correction to the inertial navigation attitude error of the missile inflight and enhance the middle-terminal phase switching probability of the missile, this paper proposes an inertial navigation inflight attitude correction algorithm based on the robust square root cubature Kalman filter (SRCKF) and establish an inertial navigation inflight attitude error estimation mode suitable for short-range and terminal phase of the tactical missile, it uses the observation information of the missile location obtained by a ground tracking radar, alongwith the SRCKF filtering and robust algorithm, to perform estimate and correction to the inertial navigation attitude error angle and to reduce the attitude error of the missile inflight. Simulation results show that the algorithm can significantly correct the attitude resolving error for the missile inflight and greatly restrain the influence of the ground radar observing gross error to the correction effect, and verify the effectiveness and the robustness of the algorithm.