To meet the demand of the high precision correction requirements of an array detector for photo-electronic response errors, a laser flat-field system based on diffuse scattering effect of nanoparticle solution was established to generate a reference light field with a high flatness. The structure and principle of the flat-field system were introduced and some key techniques involved in the design of optical system were also given. An optical fiber was used to deliver the laser into solution efficiently to reduce the backscattering light loss on the interface. By optimizing the fibers position and structure parameters of the cavity, the utilization of light energy was improved with a stable light field uniformity. Using improved Monte Carlo method, the effect of diffuse reflector cavity on system transmission was studied numerically. Finally, a laser flat field system was established by using Polytetrafluoroethylene(PTFE) materials with high reflectivity. Results show that the optimal position of the fiber depends on the cavity reflectivity. For high reflectance material, the optic port of the fiber near the cavity back can effectively enhance forward scattering. The laser flat field system provides the light field with a nonuniformity better than 0.3%, which basically meets the requirements of precision instruments for detector error correction, such as a long trace profiler.