Abstract: The process parameters of manganese phosphating process are determined by the orthogonal experimental design method;the influence of such parameters as phosphating solution acid ratio,phosphating time and phosphating temperature on the phosphating coating formation is studied and the function mechanism of each process parameter acting on the phosphating coating formation is analyzed. The results of the experiments on making-up and breaking-out of the phosphating treated couplings show the phosphating coating obtained is of excellent thread gluing resistance.