A regular part 2D measurement model based on multi-CCD is built. This measurement can be used for regular shape part such as rectangle, circle, ring and so on. The key technology of this model is discussed. And based on this model, a thin part online 2D measurement system based on double CCD is introduced. An experiment is designed and the result shows that the measurement system based on double CCD can reach high precision and fast speed. The model can be used to measure the width of cardboard on assembling line, and other kinds of big part size measurement.