Abstract: High surface energy is the main reason of moisture intimacy in SiO₂ thin film and leads to the decay of charges stored in the bulk. The doping of Pb²⁺ ions into SiO₂ film reduces the surface energy effectively, makes the surface more neutral and thus enhances its moisture-resistant ability. Moreover, the doping of Pb²⁺, Al³⁺ ions as net-work modifiers and net-work formers reinforces the structure of SiO₂ film, and adds new excellent positive charge storage capability and stability to the samples while reserving good properties of negative electret. It is indicated that surface energy reduction and net structure reinforcement are the effective way to improve the properties of SiO₂ thin film electret, and there is a good prospect for the SiO₂-PbO-Al₂O₃ compound film to become a new kind of inorganic electret material.