Laser with straight- line light pattern and uniform illumination is required in many measurement systems and laser welding systems. Instead of the traditional methods using diffractive optical elements and cylindrical lens, a free- form surface design method for laser diode source is proposed to improve the utilization efficiency of the light energy and the optical lighting effect, utilizing a free- form reflector to distribute the light uniformly in one direction and collimate the light in the orthogonal direction. Through the establishment of free surface model, constructing the partial differential equation, and solving the point cloud of surface, the shape of the freeform surface is obtained. Compared with the traditional methods in the line pattern design, the efficiency and uniformity are both significantly enhanced by this method. The simulation result shows that an illuminance uniformity is about 90% and an efficiency about 99% (without considering the reflectance loss) are achieved within 150° of the spread angle.