Abstract: In order to better evaluate the microstructure of free cementite in automobile sheet products, three methods for evaluating cementite were introduced in combination with the evaluation methods in relevant standards at home and abroad, namely, grade evaluation method, quantitative method and maximum limited size method. The evaluation contents of each method were described in detail, and three methods were used to evaluate the free cementite in cold rolled carbon steel sheet and steel strip, which was convenient for readers to better understand and use, and provided a reliable microscopic evaluation method for the improvement of product quality such as automobile sheet.