Abstract: A novel wideband cavity-backed slot antenna operating at X band is proposed. The band width and gain of the antenna are significantly increased by multi-layer dielectric resonator loading. The proposed antenna has a 40％-10 dB return loss bandwidth at a center frequency of 10 GHz and the gain within this band are 5~9.5 dBi which is 2~3 dB higher than those without the multi-layer dielectric resonator loading. The measurement results agree with simulations well thus demonstrates the design is correct and effective.