Abstract: Based on the secondary geodesic line method and the geometric characteristic of parabolic reflector, the approximate secondary geodesic line method was obtained. To get the expansion boundary of the space film in plane, polynomial fitting for the discrete point on the tailoring line was conducted. And the effects of the tailoring step length and tailoring film projection angle were analyzed. The results showed that step length affects the accuracy of tailoring less than projection angle. The error was only 0.27% when the projection angle was 10. The deformation analysis of the reflector was achieved by using beam structure for equivalence of the thin film. The equivalent method could avoid large deformation caused by the force out of thin film. Load test for the reflector was carried to verify the correct of the equivalent method. Spotlight experiment was conducted based on the tailoring analysis and deformation research. The spotlight result is good. The tailoring analysis method and equivalence method can be the bases of the design for large reflector.