Based on the development of the cleaner production assessment system of iron and steel industry in China, the composition and application scope of the technical documents of the current assessment system were introduced. Taking integrated iron and steel enterprises built after 2018 in Jiangsu and Hebei as examples, the practical application of the system was analyzed. The results show that the current cleaner production assessment system of iron and steel industry is relatively rational, but still suffered from some shortcomings, such as the obsolescence of technical indicators, failure to cover the whole process, and lack of information technology sourcing.