Environment-friendly pickling and passivation process of welded pipes of 304 stainless steel was studied by means of orthogonal test, its passivation influence on welded pipes of 304 stainless steel was evaluated with electrochemical test.The best passivation formula selected from the orthogonal test is 3% citric acid, 5% hydrogen peroxide, 2. 5% absolute ethyl alcohol, 40 ℃, 30 min, and could obviously improve the pitting corrosion resistance of welded pipes of 304 stainless steel.