The method of spatial convolution has been applied to analyze the imaging process of CCD imaging system, which involves optical imaging process and CCD integral sampling process. The way of changing the ratio between Ground Resolution Distance (GRD) and Ground Sampled Distance (GSD) (Kell coefficient) to improve the image resolution was introduced. Imaging process of the target was simulated with different Kell coefficient values. The method of comparing the mean modulation values in a period of the images on CCD which was regarded as the evaluation criteria was proposed to evaluate the image quality of the CCD aerial surveying camera. The results show that when Kell coefficient equals 2.8, the target characteristics can be distinguished.