The results, albumen thermo solidification experiment and leaking dynamometer are used to investigate the radiant power density field radiated from a microwave antenna, show that the microwave field radiated from the monopole antennas, which are used usually in clinical treatments now, is not uniform. The radiation intensity near the root part of the antenna is strong,and near the top part, which is close to affected part, is rather weak. The suggests that monopole antenna was inefficient and was not ideal as a microwave antenna for in body. For the helical antenna, however near the top part the radiation intensity was rather strong, and the radiation was concentrative and efficient. Experiment results and many clinical examples suggest that the helical microwave antenna is a dependable, stable, safe and efficient one, and has a wide applicant future in clinical practice.