The coating thickness is an important index in the test of the finished products of the color coating board. It directly affects other properties of the color coating board. Its accuracy not only affects the quality of the color coating board, but also affects the production cost.The cold rolling mill color coating production line estimates the amount of coating used, and the production function department reserves the coating according to the estimated amount and arranges the production plan. But in the actual production, the true amount of coating is determined by the test room through the test coating thickness result. Recently, there is a big difference between the estimated amount of paint and the real amount of paint in the color coating production line of cold rolling mill. Based on a large number of test data, this paper analyzes the substrate, the weight of passivation film and the detection method of the color coating plate, which provides a basis for improving the accuracy of the detection results of the color coating plate thickness.