Laser scanning system is widely used in high precision systems, such as laser machining and imaging. The optical quality is the final index of manufacture process. In mass production, the tolerance analysis of the optical system is needed to meet the demand of use and reduce processing cost. For example, the laser scanning system is simulated by the unified field optical analysis. The position tolerance and rotation tolerance of each workpiece of the system is analyzed based on the optical properties of the laser scanning systems. The overall system meets the design and uses requirements through tolerance constraints for each workpiece. The measurement platform is built, and the measurement result is consistent with the analysis of unified field tracing.