The invention relates to a method for increasing the movement stability of a driving mechanism of a spaceborne antenna with a gap. The method is based on multibody system dynamics theories, flexible multibody system dynamics and a kinematic pair gap contact collision model. A spaceborne antenna driving mechanism dynamics model which taking a kinematic pair gap into consideration is established, and the influence of the gap on the dynamic characteristics of a reflecting plane of the spaceborne antenna is analyzed through value simulation. Minimizing the maximal peak value of movement acceleration jitter of the reflecting plane of the spaceborne antenna is taken as an optimization target. The element contact collision parameters of the kinematic pair with a gap are optimized without changing the basic structural parameters of the driving mechanism of the spaceborne antenna, and the auxiliary material of the elements of kinematic pair with a gap is selected to improve the movement stability of the driving mechanism of the spaceborne antenna. The element contact collision parameters of a kinematic pair with a gap are optimized, and proper auxiliary material of the kinematic pair is selected to substantially reduce the impact effect caused by gap contact collision of the kinematic pair, and reduce the influence of the gap on the movement stability of the driving mechanism of a spaceborne antenna. The method is simple, feasible and practical, and can be widely applicable to driving mechanisms of various spacecrafts.