When applying OPC techniques in manufacturing of complex and delicate integrated circuits, any improvement in accuracy of computing aerial images is crucial. Simulation accuracy is demanded more and more today as the feature sizes are being decrease, while the computation speed haw to be kept in a reasonable pace. As a consequence, loss of symmetry in simulation appears to be more problematic and has begun to require attention. Quantization, sampling and intensive iterative computation are all sources of the problem. In this paper, we study the problem of symmetry preservation, present method of symmetry enhancement, and apply the method in process simulation. The computing results of this method are satisfactory and promising, having laid a foundation for future study on its application in OPC, and of its effect on the performance of certain symmetric IC patterns.