Abstract: A new kind of inorganic electret composite: SiO₂-Ta₂ O₅-B₂ O₃-RO has been developed via high temperature sintering and elements selecting and matching on the silicon wafer. The test results showed that the sample was a microcrystalline structure while its dielectric constant was up to ～ 2000. The surface potential which was almost equal to the grid voltage could be achieved after Constant-Voltage-Charging,and Thermal Simulated Discharge TSD showed that the negative and positive current peaks were located at T = 240℃ symmetrically and fixedly while the activation energy of the trap was about ～ 1.22 eV. It can be concluded that the Si O₂-Ta₂ O₅-B₂ O₃-RO was a novel microcrystalline electret composite with good capability of both negative and positive charge storage.