Polyimides (PI) have desirable properties for use in the electrical and electronics industry because they are a group of excellent high temperature heat-resistant organic polymers and have good planarization capability, excellent chemical resistance, low relative permitivity and electrical insulating properties. A dielectric model for PI is required to understand the degradation due to various stresses such as high temperature and high humidity. In this study, manufacturing a metal- polyimide-metal (MIM) structure and performing measurements on this MIM structure, changes observed in the complex permittivity of PI due to high temperature and humidity (RH) aging are modeled using a Debye-type function.