Abstract: Particle swarm optimization (PSO) technique is applied to design a five-lens system.The optical merit function composed of spherical aberrations, an image distance, distortions, field curvatures, comas and light dispersion values, were employed as fitness functions of the particle swarm algorithm. By using this function automatic searching for the optimal design, a simple five-lens system was carried out. Comparisons in terms of spherical aberrations, distortions, field curvatures, comas and light dispersion values were performed between a five-lens system designed with PSO and a five-lens system from ZEBASE. The result shows that spherical aberrations, distortions, meridional field curvatures, sagittal field curvatures, sagittal light dispersion values of a five-lens system designed with PSO are smaller, and meridional light dispersion values, meridional comas, sagittal comas of a five-lens system from ZEBASE are smaller. The example for a five-lens system design using particle swarm algorithm indicates that PSO can overcome the shortcomings of the modern optical design software which highly depends on an initial structure input by the user and can create arbitrarily search ranges of structure parameters, which is an important step towards automatic design with artificial intelligence.