As two parameters of evaluating automobile assembly quality, gap and flush directly affects the overall appearance, sealing, switching fluency and wind noise of automobile body. Therefore, clearance surface difference of automobile assembly parts must be strictly controlled.Because of the complexity in the actual measurement of clearance surface difference, this paper presents a method of measurement of gap and flush based on virtual matching. The experimental results show that the measurement method is basically consistent with the actual measurement, where the efficiency is greatly improved.