Epoxy resin is widely used in the packaging insulation for high-voltage electrical equipment and integrated electronic devices. Its post curing effect during long-term storage may affect the material performance and storage reliability of epoxy packaging products. In this work, the curing temperature of epoxy resin was further enhanced based on the conventional curing process, which is used to simulate the post curing reaction during storage, and its effect on the properties was studied. The results show that, the post curing does not significantly change the molecular structure of epoxy resin, but has a modest effect on the thermal, mechanical and electrical properties, such as the enhancement of glass transition temperature, the increase of storage modulus (in glassy state) and loss modulus, the slight decrease of relative permittivity and dielectric loss, and the improvement of pulsed breakdown field. This work could support the storage reliability assessment of epoxy packaging products.