Abstract: An ultra wideband pulse transmitting antenna based on bow tie antenna was designed. The metal cavity was used to improve the directivity of the antenna and played a shielding role. The absorbing material in the cavity reduce the reflection of electromagnetic wave in metal cavity, and improve the antenna frequency domain characteristics and time domain signal. The finite element electromagnetic simulation software HFSS was used to design the antenna model and optimizate the parameters of antenna. Compared with the absorbing materials and metal cavities, the parameters of the actual antenna are effectively improved. The center frequency of the antenna is lower, and the bandwidth below -10 dB increases from 100 MHz to 200 MHz. The width of the pulse signal is reduced, the signal tailing is eliminated. The actual disturbance above ground was shielded effectively. The detection accuracy is also improved, and the direct wave and reflecting waves are effectively separated. Compared with the atenna without shielding cavity, the detection results are greatly improved.