The BR-II-3 manganese-based surface conditioning agent may be used for surface conditioning prior to manganese-based phosphorizing of steel. When subjected to such process, the steel surface will be covered with numerous fine manganese-phosphate crystals so that the crystal nucleus necessary for manganese-based phosphorizing increases greatly in number. This may not only accelerate phosphorization and properly lower the temperature of phosphorization, but also prevent big-size crystals from being generated. As a result, the resulting phosphate has improved fineness and evenness.