Q235 Steel specimen was phosphated at room temperature in the Mn-Ca-Ba phosphating solution consisting of manganese dihydrogen phosphate, calcium nitrate, barium nitrate and sodium molybdate. Washing-free, colorful phosphate coating was formed after natural drying for 3 hours. The effect of pH value, temperature, treatment time and the lifetime of phosphating solution on the properties of the phosphate coating was investigated. Moreover, the morphology and component of the phosphate coating were analyzed. The results show that continuous and compact phosphate coating is obtained when the specimen is phosphated for 8 ~ 10 min under 5 ~ 40 益 with phosphating solution, whose pH value is 2 . 3 ~ 2 . 8 . The particles of the phosphate coating are very fine. The phosphating coating is composed of phosphate of Fe, Mn, Ca and Ba and a little of molybdate. The time of copper sulphate solution corrosion resistance is more than 85 s, and the weight of coating is around 0 . 9 g /m². The adhesion of the coating reaches 1 grade after being sprayed with iron-red epoxy primer.