Optical simulations based on transfer matrix method, combined with Matlab have been performed to investigate optical properties of inverted polymer solar cell (IPSC). Effects of thickness, angle of incidence and structure on optical performance of IPSC are studied theoretically. Simulations reveal that optical absorption is mainly dependent on active thickness and has faint decrease as thickness of electron transport layer and hole transport layer increase, respectively. Path length of light inside a solar cell increases so that more light is absorbed. The absorption rate reachs its maximum under the angle of 40°. However, as with other optical effects the absorption rate reduced with the increase of angle, when the angles above 40°; Furthermore, simulations demonstrate optical electric field for p-polarized light is discontinuous at boundaries. A microcavity device which has been constructed by a dioxide (TiO2) layer into the basic structure can significantly enhance light absorption due to the optical resonance effect.