Abstract: An ultra-wideband end-fire antenna that can operate in the L-Ku band is presented in this paper. The antenna is consisted of radiation gap printed plate, reflective cavity, and cavity support material, etc. The backward radiation can be suppressed by adding a cavity and load matching below the radiation printed board of the antenna. Adding slot unit between the slot can adjust the amplitude and phase matching of adjacent antenna units to enhance the end-fire performance. The impedance matching feeding can be realized by using coplanar waveguide conversion coaxial connector at the top of the antenna. A simulation analysis of the adiation performance of the proposed ultra-antenna end-fire antenna is conducted, and the results show that the antenna can achieve 18-octave bandwidth and has excellent port matching and end-fire characteristics, S11 is less than -10 dB, and the angle between E-plane and horizontal plane is less than 30°. The measured result indicates that it has good consistency with the simulation results.