Viewing angles of liquid crystal display (LCD) can be improved and three primary colors dispersion characteristics of red-green-blue (RGB) can be compensated by modulating polarized light with retardation film. Electro-optical characteristics of three primary colors of capacitive touch panel (CTP) LCD with and without retardation film under different driving voltages at vertical direction with different viewing angles are tested by WGD-6 optical multi-channel analyzer respectively. Experimental results show that as viewing angles increase, relative light intensity of green primary color of CTP LCD at vertical direction deviates seriously from that of red and blue primary colors. It results in obvious color deviation. Relative light intensity difference of three primary colors is reduced effectively after a retardation film is coated on the surface of CTP-LCD. So color correction and viewing angle increment can be achieved.