In order to realize the demand of low power sensor for pneumatic system, a new type of magneticassisted piezoelectric energy harvester was proposed and it can promote the efficiency of harvesting the dynamic high air. The noncontact force between the magnets was used as magnetic induced prestress acted on the center of the piezoelectric circular diaphragm. The magnetic induced prestress can adjust the surface charge distribution of the piezoelectric circular diaphragm when the dynamic air pressure acted on the piezoelectric circular diaphragm. The simulation research showed that the repulsive force increased the output power of the magneticassisted piezoelectric plate harvester, while the attractive force decreased the output power of the magneticassisted piezoelectric plate harvester. The diameter and thickness of piezoelectric unimorph were 22mm and 0.23mm, respectively. The diameter and distance of cylinder were 63mm and 150mm, respectively, and the prototype of the magneticassisted piezoelectric plate harvester was fabricated. The test system was built to research the rules and performances of the magneticassisted piezoelectric plate harvester. In the test, the pressure, cycle, flow and the magnets distances were adjusted. Experimental results showed that the instantaneous power was 1.39mW when the optimal load resistance was 0.87MΩ, and the output power of the generator was promoted 12.6%, while the magnetic induced prestress was only about 0.6% of the hyperbaric air load. Therefore, the magnetic induced prestress can effectively improve the efficiency of the dynamic high air in the pneumatic system.