The bow-tie antenna, which is widely used in impulse ground penetrating radar (GPR), has very low radiating efficiency. It is because that nearly 70% of the radiated energy exists as the form of end reflection, which is obstructive to probing objects. In order to keep the probing ability, the remarkable energy in end reflections is usually dissipated by resistive loading. Through the current research, it was found that, if the exciting pulse is bipolar and monocycle, the radiation efficiency can be significantly improved by utilizing the energy in end reflection, and the improvement can be implemented by optimizing the antenna length. The simulated results show that the radiation efficiency can be increased by nearly 100%. The measured results validate the proposed method again. Additionally, the proposed method is easy to be carried out in applications and of great use.