Abstract: To study the influence of the different CuO concentration rates on the resonance angle,a novel surface plasmon resonance(SPR) optical sensor coated a combined Ag and SnO2(dropped by CuO) film is proposed.Four-layer films Ag(50nm),SnO2(50nm),CuO and SnO2(50nm) were prepared deposition on rutile prism in turn by means of RF-reactive-sputtering,and the thickness of the CuO was various with the concentration rate,and the combined film was formed after being annealed.The SPR experiments show that,when the concentration rates of the CuO are 0,0.01 and 0.05,the resonance angles are 59.61°,60.52°和61.3°,respectively.The faster concentration rate of the CuO,the larger of the resonance angle.