Abstract: The hazards from Fe²⁺ in the phosphorization solution for cold-drawn steel tubes and elements responsible therefor are investigated, and mechanism concerning depression of the said Fe²⁺ described.Experiments upon depression of Fe²⁺ in the phosphorization solution with NaClO₃ were carried out, which led to the conclusion that adding NaClO₃ into the solution at the concentration by weight of 0.5g/L could produce effective depression, hence increased economy.Also introduced are the key points of the operation.