To increase its authority in rarefied air and improve its environmental suitability in near space flow control, the characteristics of plasma synthetic jet actuator with cavity pressurization were investigated. A simplified model was proposed to analyze the cavity pressurization performance. The calculation showed that the chamber pressure is effectively improved by the high pressure air supply. Besides, the chamber pressure shows good following characteristics, which provide a novel method to control plasma synthetic jet intensity. The experimental system of plasma synthetic jet actuator with cavity pressurization was built. The measured chamber pressure was in good agreement with the calculated result, with a maximum error of 2.6 %. The high-speed schlieren visualization showed that the jet front velocity is significantly improved with cavity pressurization. The peak velocity increases from 256 m/s to 507 m/s.