In this study, we proposed a micro-mechanical model to describe the effects of temperature and UV radiation on the constitutive behavior of elastomers. Specifically, the focus of this model is on the effects of photo-oxidative aging on the mechanical response of elastomers and their inelastic responses such as permanent set and Mullins effect. With regard to experimental studies on the nature of chemical reactions during aging, chain scission and bond creation happens simultaneously. However, the rate of these two are different. Thus, during photo-oxidative aging, cross-link density might increase or decrease depending on the rate of reactions. To make things even more interesting, these rates are functions of temperature, UV radiation intensity and time. Thus, during aging, the elastomer might become harder, softer or in more complicated cases, change between hardening and softening in due time. Therefore, strain energy of the polymer matrix should be calculated with regard to time, temperature and UV radiation intensity. Using this experimental analysis, we proposed a new micro-mechanical model. Since separating the effects of thermo-oxidation and photo-oxidation seemed impossible, the proposed model is a generalization of another micro-mechanical model for thermo-oxidative aging. Therefore, the model has two sets of parameters. One that its components only are a function of temperature and another that are a function of both temperature and UV radiation intensity. To validate the model, comprehensive set of experimental data has been conducted. The proposed model shows promising result with great precision.