The invention relates to an antenna array design preprocessing method based on a complementary structure. The method comprises the following steps: (1) determining the center frequency f0H of the antenna working with high working frequency, the center frequency f0L of the antenna working with low working frequency, the minimum array element spacing dH of the antenna with high working frequency, and the minimum array element spacing dL of the antenna with low working frequency; step (2) determining the arrangement mode of the antenna array with low working frequency; step (3) determining a mixed distribution area of a double-frequency antenna array in a phased array radar array plane; step (4) acquiring the size specification and the number of the antenna array complementary structures withhigh frequency; step (5) and storing the result into a database. According to the preprocessing method disclosed by the invention, the size limitation and specification limitation of the double-frequency common-aperture phased arrays on the TR components can be reduced, the array element density and the TR component density can be effectively reduced, and the whole array can be more easily engineered and designed.