In this paper, an ultrawideband (UWB) and high gain horn antenna with lens is proposed for microwave communication system, which is composed of Eplane horn antenna, a dielectric spherical lens and double wedge metal ridge. The proposed antenna is fed by coaxial feed, which is simulated by high frequency structure simulator (HFSS) software. The simulation results show that the double wedge metal ridge can effectively increase the bandwidth of the horn antenna, and the effective frequency bandwidth reaches 2~12 GHz. When only the double metal ridge is used to improve the performance of the horn antenna, the gain of the horn antenna will decrease. In this work, a spherical dielectric lens is used to compensate for the negative effects of double wedge metal ridge on the horn antenna gain. According to the simulated results, the dielectric lens can effectively improve the gain of the horn antenna in the working frequency band. With the proposed lens and a metal ridge structure, the horn antenna has ultrawideband, high gain and strong directional radiation performance, which can be applied to various communication systems.