The intersection issues between the reflected light and the incident light are transformd into the intersection problems between the reflected light and the plane containing the incident light, and the line-plane model is constructed. The point light source is used to replace the traditional continuous surface light source, and the incident light plane is determined by detecting the projected lights of two or more light source points on the incident light. Then the mirror point is determined by the intersection between the reflected light and the incident light plane. The calibration method for line-plane deflectometry is proposed on the basis of the mirror calibration method, which can be used for specular measurement with only once calibration. The effect of the posed relationship on reconstruction accuracy of the system is analyzed in simulations. The maximum error of system measurement is 0.25 mm, the root mean square error is 0.073 mm. Experiments verify the feasibility of the proposed methods, and the experimental results show that the method has high accuracy.