Abstract: A new flow injection system using UV detector and adopting an on-line adsorption column to eliminate the interference of excipients is proposed for the content uniformity test of codeine phosphate tablets.The results obtained with this system agree well with those by the conventional method.The proposed system with a sample volume of 60 μl,sampling frequency of 60/h and precision of 0.8%(RSD,n=40 )is suitable for the content uniformity test and assay of codeine tablets as well as those of other dosage forms.