To realize the automatic sun-tracking based on four-quadrant detector, the working principle of four-quadrant detector is firstly analyzed and the reason of selecting four-quadrant detector is explained. The setup based on four-quadrant detector for sun-tracking is introduced, the possibility of deviation influence, such as geometry position of the sun spot, installation position between aperture iris and four-quadrant detector is deeply investigated, the consistency between four-quadrant detector and its I－V conversion circuit is analyed, and the influence of consistency on tracking precision is evaluated. The reason and rationality of deviation existence on four-quadrant detector voltage for sun-tracking are introduced. The experiment demonstrated that the designed device based on four-quadrant detector is suitable for high-precision sun-tracking.