The insulation layer effect on electro-optic properties of fringe field switching (FFS) liquid crystal display (LCD) is simulated in this paper. The simulation results show that the threshold voltage and operating voltage rise when the thickness of insulation layer is increased, while variation of the insulation layer thickness has no affect on transmittance, response time, and optical properties. So decreasing the thickness of insulation layer means easier driving and more power reduction. This rule may be useful for device design and industrial production.