In order to realize the purpose of the tail cover being side-thrown away from the launch axis during the second ignition of the cold catapult missile, a new type of shroud throwing scheme was proposed: the eccentric tail cover and the nozzle outlet were connected by a sealing plug, and the gas jet was used as the power source to realize the side-throwing separation. Considering the influence of different centroid positions and horizontal lateral winds on the separation process, a three-dimensional tail mask separation model was established, combined with the overlapping dynamic mesh technology, the fluid control equation and the rigid body six-degree-of-freedom motion equation were coupled, and the tail cover separation process was numerically simulated. The variation curve of the motion characteristics of the tail cover when it is impacted by the jet and the interference characteristics of the tail cover on the flow field of the gas jet are obtained. The results show that the scheme can achieve the purpose of lateral throwing of the tail cover away from the emission axis. With the increase of the degree of centroid bias, it is beneficial for the jet state at the axis to be stable first. When the centroid position is greater than one-half radius, the jet has a greater accelerating rotation effect on the tail cover than the translational rotation, which increases the instability of the tail cover during the movement, and the tail cover tends to be close to the axis in the later stage of separation. The horizontal lateral wind is conducive to the tail cover to stay away from the axis, and the trend of moving away from the axis is more obvious with the increase of wind speed.