Abstract: A novel chessboard composite surface composed of artificial magnetic conductor(AMC)and perfect electric conductor(PEC)cells is proposed to realize waveguide slot antenna with enhanced gain and reduced backward radar cross-section(RCS).The improved radiation and backscattering performance of the antenna are due to the secondary radiation source and anti-phase cancellation,respectively. Measured results show that the antenna gain in both E-plane and H-plane is increased by at least 5 dB with the proposed structure.Meanwhile,the backward RCS of the antenna is reduced by at least 8 dB in the operating frequency band.