The invention belongs to the field of a radar sidelobe cancellation antenna and particularly relates to a method for improving the coverage effect of a P-band radar sidelobe cancellation antenna. According to the method, a first layer annular support, a first microstrip plate, a second layer annular support, a third layer annular support, a second microstrip plate, a fourth layer annular support,a fifth layer annular support, a third microstrip plate, a sixth layer annular support, a seventh layer annular support, a fourth microstrip plate, an eighth layer annular support, a one-to-four phaseweighted power division network and an antenna base, wherein the microstrip plates are eight microstrip dipole antennas integrated on the same base plate through the one-to-eight power division network. The method is advantaged in that problems of non-high coverage efficiency, over-large azimuth amplitude fluctuation and poor portability existing in a sidelobe cancellation antenna in the prior art are solved.