AlxGa1-xN photocathode was prepared by MOCVD and the reflectivity, transmittance, and absorptivity were test. Based on thin film principle, optical model of t-mode AlxGa1-xN photocathodes was built, and then optical properties and quantum efficiencies were simulated. Results show that AlxGa1-xN photocathodes satisfy the need of detectors with “solar blind” property when the Al component is larger than 0.250. There is an optimal thickness of AlxGa1-xN layer to obtain highest quantum efficiency, and the optimal thickness is 0.3μm. There is close relation between absorptivity and quantum efficiency, which is in good agreement with the “three-step” model. This work gives a reference for the design and preparation of AlxGa1-xN photocathodes.