The production of singlet delta oxygen by radio frequency (RF) discharge is studied experimentally. The trends of the relative yields of singlet delta oxygen as functions of different doped gases, different electrode gaps and He/O2 ratios are obtained. The dependences of singlet delta oxygen yields and electric efficiency on the specific input energy are analyzed. The experimental results show that the relative yield of singlet delta oxygen increases obviously by adding nitric oxide or gaseous mercury. Homogeneous glow discharges at high pressure can be achieved with the total pressure of 22.6 kPa and the oxygen partial pressure up to 4.0 kPa by reducing the electrode gap. The optimum relative yield of singlet delta oxygen is obtained with the specific input energy of 150~400 J/mmol oxygen, and the optimum electric efficiency is obtained with the specific input energy of 150 J/mmol oxygen.