Abstract: Based on the conventional fixed-focus lens and the aspherical principles, a triplet fixed-focus lens assembly for the digital camera was simulated with the optical system design software CODE V to meet the needs for the compactness, high transmissivity, excellent optical performance and low cost . In the lens assembly, plastic lenses were chosen instead of glass/plastic hybrid or all glass lenses for the cost and production consideration. The back focal length of the digital camera was increased by 0.8116 mm with the lens assembly. Therefore, it can guarantee a better performance for the telecentric beam path. The profiles of the three lenses were designed as aspheric surfaces so as to correct the aberration and ensure the excellent optical performance.