The BR-III-A ultra-concentrated and low-cost phosphorizing liquid works under medium or low temperature and with little dregs and quick effect. Through phosphorizing treatment, it may generate a thin, dense and even zinc-based phosphate coating on the steel surface. The product is widely used for treatment of steel prior to painting. The phosphate coating generated in this way may improve the adhesive force between the paint and the steel body as well as the anticorrosion performance of the paint.