Abstract: In this paper, a novel unit cell of multi-layers transmission array(TA) is proposed. The unit cell is composed of C-shaped slot structure. After the simulation, the unit cell achieves a phase shift change of -503°-167° and get a good phase curve in Ku band. Based on the phase compensation theory, a TA is designed with the rectangular horn antenna as the source. The simulation results show that the gain can reach 24.74 dBi at 12.5 GHz. The aperture efficiency and 1 dB gain bandwidth of the antenna are 44.4% and 17% respectively. The TA is fabricated and tested, and a good agreement is achieved between simulation results and the test results.TA has the characteristics of high gain and wide bandwidth. It is also instructive to construct a practical TA radar antenna.