This study investigated the electro-optic characteristics of VAN ¡]vertical-alignment nematic¡^liquid crystal device in passive mode, and tried to present the advantage of high contrast ratio which belongs to VA mode. The experiment consisted of three parts: 1. Change different cell thickness¡]d = 12£gm¡B6£gm¡B4.9£gm¡^. 2. Chang LC with the different value of dielectric¡]£G£`= -3.7¡B-6.1¡^. 3. Chang LC with different refraction anisotropy¡]£Gn = 0.15¡B0.078¡^. We drive those samples with different number of duty in passive mode, and to measure the electro-optic characteristics, including VT curve, response time, and contrast ratio. We knew that STN¡]Super Twist Nematic LCD¡^has the drawbacks of lower contrast ratio, higher operational voltage and slower response time within higher duty in passive mode. And the same problem comes with VAN in passive-drive mode, although it is said VAN has the high performance of contrast ratio. The contrast ratio is worse then STN when driving in higher duty. As a result of VAN is kind of ECB mode, its transparency has a big matter with light retardation. We find that in the same condition of driving duty, the value of cell gap or the £Gn become larger, the value of the sharpness and the contrast ratio become larger.