In order to realize the compact monopulse variable polarization antenna, the development of a Ka-band monopulse variable polarization antenna is presented, based on polarization synthesis theory. The loss of the feed network is reduced by using space power combing technique. This kind of microstrip array antenna consists of several linearly polarized subarrays of rotational symmetry, and change the polarization mode by adjusting the amplitude and phase of each subarray. The simulation of the four subarrays shows that this antenna using sequential rotation method has great advantages, such as simple, high polarization purity, low loss and so on. Analysis of the effects of the antenna beam caused by amplitude and phase inconsistency of each subarray is carried on, and the actual requirement of amplitude and phase consistency is put forward.