For the purpose of acquiring IC micro-topography accurately, fuzzy gray theory is used for quantitative evaluating the influence factors of IC chip’s image characteristics. Through selecting different influence factors in the process of image acquiring and establishing the factor-parameters array, a mathematical model of fuzzy gray evaluating system is structured. After calculating the fuzzy gray relational degree between the factor-parameters and the image characteristics, the external influence on image is quantized. By experiment and comparison the relational degree is quantitative analyzed and the influence tendency is chart-illustrated, thus research conclusions and referential suggestions are reached. It provides theoretical foundation and technical preparation for IC image sampling condition’s selection and adjustment.