The active laser detection based on cat-eye effect is used as the application background, according to the defect of usual analytical method to research the cat-eye effect echo characteristics. The analytical method of optical window mapping is proposed to analyze beam transformation via matrix optics, and the model of echo shape and energy is built on the condition that the reflecting element is defocused and the incident beam is not normal incidence. It resolves the problem that the physical significance of echo divergence angle is wrong and the echo spatial dimension cannot be figured out. The theoretical model is certificated by experiment through setting the ideal cat-eye optical system. The calculation results are in good agreement with the experimental results. The proposed model and related results are very important to develop active laser detection and anti-detection technology based on cat-eye effect.