Abstract: A new approach to the continuous monitoring in situ of the dissolution rate ofmetronidazole tablets using fiber-optic chemical sensor( FOCS )without fiItering and sampling isreported.It provided increasing amount of information on the dissolution test of tablets.The range ofrecovery(%)of the proposed method was 99.7～102.3%,The precision(RSD)of within-day andday-to-day was less than 4%.The three parameter biexponential(TPBE)function was used to fit thedissolution curve,The results of measurement for the dissolution test of metronidazole tablets usingFOCS were in agreement with those of USP(XXII) method,and the FOCS methed was simple andaccurate。