Abstract: A series of experiments have been performed to study the radiation characteristics of single-source monopole plasma antenna. The radiation intensity and pattern were measured carefully, and then the antennas main lobe beamwidth and direction factor were derived. Through the comparison with metal antenna, the radiation efficiency of plasma antenna was fingered out. The impedance of the antenna was also measured and analyzed. The results show that plasma antenna has a similar radiation pattern and impedance as metal antenna does, and in most cases its direction factor is better than the laters. However, its radiation efficiency is lower and its stability is weaker.