Abstract: A clean production technology of sodium sulfoxylate formaldehyde by one-step process with sodium pyrosulfite,zinc powder and formaldehyde as raw materials was studied in detail.The optimum operation conditions were：n（Na<SUB>2</SUB>S<SUB>2</SUB>O<SUB>5</SUB>）∶n（Zn）≈1∶2.5,n（Na<SUB>2</SUB>S<SUB>2</SUB>O<SUB>5</SUB>）∶n（CH<SUB>2</SUB>O）≈1∶2.1,sodium bisulfite solution′s pH is 3.3～3.6,activation temperature is less than (≤)45 ℃,highest temperature 97～102 ℃ and pyroreaction time is 1～1.5 h.The capacity of the first plant of sodium sulfoxylate formaldehyde by one-step process in China has reached 6 000 t/a.The production conditions showed that the conversion rate of sodium pyrosulfite was 87.0%;the yield of formaldehyde was 85.9%;zinc was made into zinc oxide product and its yield was 99.5%;the plant conditions were good;there was not too much waste produced in the process;and the waste treatment was not difficult and it was easy to meet the discharge standard.It is obvious that the one-step process is a clean production technology in contrast to the traditional three-step process.