To achieve a substantial retroreflection reduction accompanied with a superior anti-laser blinding property without suffering significant degradations in imaging quality, a novel defocused wavefront coding imaging system is designed. Relevant studies have been carried out around its mechanism in both anti-laser reconnaissance and anti-blinding. According to the Fresnel-Kirchhoff diffraction theory, the laser propagation through the defocused wavefront coding system is theoretically modeled. In this model, the transmission characteristics along with the laser defense performance are further evaluated, and the parameter optimization rules are proposed. Results show that by reducing the echo-detector receiving power and the maximum incident power per pixel by more than two and one order of magnitude respectively, the defocused wavefront coding system can greatly improve the performance of anti-laser reconnaissance and anti-blinding while maintaining good imaging quality.