<p>In this study, a Scanning Electron Microscope Optical Simulator (SEMOS) was developed to provide an intuitive and quantitative understanding of electron-beam optics and to optimize lens operating parameters for improved SEM performance. The simulator integrates instrumental data–including electron source characteristics, lens geometries, and operating conditions—and performs electron-beam ray-tracing simulations to calculate key optical indicators such as probe size, probe current, and attainable resolution. The optical parameters of the condenser and objective lenses were derived using a commercial electron-optical design program, and SEMOS was subsequently applied to optimize the SPOT table, which stores predefined lens configurations in commercial SEMs. The optimized SPOT table improved the focusing consistency and resolution linearity across operational modes, demonstrating the practical applicability of SEMOS for both SEM users and developers. This work establishes a systematic simulation framework for electron-optical analysis and operational optimization in modern scanning electron microscopy.</p>