Abstract: This paper studies the automic analysis on the production line of sodium hypophosphite during plating baths of electroless nickel plating process.Using the principle of continuous flow spectrophotometry,the instrument of automic analysis on production line is developed.The regression equation between the sodium hypophosphite concentration and the logarithm of incident light's transmitivity is abtained through the standard concentration of sodium hypophosphite being determined.The standard deviaTPPtion of the instrument is less than 2% and the error comparing to the chemistic analytic method is less than 4%.The analytic time only takes 6 minutes.The instrument is suitble for the automic analysis of sodium hypophosphite on electroless nickel plating production line.