A design for freeform surface lens with ultra-high light efficiency and small light-gathering angle is proposed to realize uniform light distribution for LED light source. A freeform surface differential equation is constructed based on the refraction phenomenon when light is passing through the lens. High accuracy algorithm is applied to obtaining parameters of the lens surface. The light distribution effect achieved from the proposed method is with smaller light gathering angle and higher light efficiency than those obtained from the traditional lens. A three-dimensional model is established by the professional software. The thickness of the lens can be reduced by cutting a sphere inside the lens model. The simulation in real application environment verifies the validity and the reliability of the scheme.