A design method of aspherical surface for a panoramic imaging system with two mirrors was proposed based on Multi-population Genetic Algorithms(MPGA).To eliminate the astigmatisms induced by mirrors and to improve the image resolution,an algebraic expression of astigmatism for panoramic imagers was induced based on the generalized Coddington equation and the theory of geometric optics. Then, an optimization process for mirror profile design was proposed to eliminate the astigmatism and to provide a purposely-designed projection formula with aid of the MPGA. A series of polynomial expressions of aspherical surfaces were obtained and procedures of the design were presented. In order to facilitate ray tracing and aberration calculation,an even asphere surface model was established by using a hybrid scheme combining the MPGA and the damped least squares. Finally,a prototype of the omnidirectional panoramic imager with f′ of -1.2 mm and F/# 1.5 for 360°(35~90°) was developed,which can provide clear panoramic ring images.