A thin film dielectric layer was used to separate the floating electrode and the mode control electrode. The floating electrode and the mode control electrode were on the same side of the substrate, which avoided the restriction of using a thin substrate. Comsol Multiphysics software was used to simulate the influence of the square resistance of floating electrode and the thickness of thin film on the wavefront error of liquid crystal lens. For the liquid crystal lens with a diameter of 2 mm, when the square resistance of floating electrode varies from 150 Ω·□^-1 to 300 MΩ·□^-1, the wavefront error of liquid crystal lens decreases first and then increases, and reaches a minimum value at 40 MΩ·□^-1. When the thickness of the dielectric layer varies from 50 nm to 5 000 nm, the square resistance of the floating electrode with the smallest wavefront error decreases from 50 MΩ·□^-1 to 2 MΩ·□^-1, and the optimal square resistance parameters decrease monotonically. When the square resistance of floating electrode is 40 MΩ·□^-1 and the thickness of dielectric layer is 250 nm, the focusing characteristics and wavefront error characteristics of liquid crystal lens are studied. When the focal length varies from 250 mm to infinity, the maximum root mean square error of wavefront at 589 nm is 0.041 2 μm, less than λ/14, which satisfy the Marechal criterion.