Abstract: Base on the significant fluorescence-quenching effect of Mo(Ⅵ) on fluorescence emitted by isoprenalinum in an acetate buffer medium of pH 5.6,a fluorospectrophotometric method for determination of Mo(Ⅵ) was proposed.Linear relationship between the magnitude of decrease in fluorescence intensity and concentration of molybdenum was obtained over the range 0.01 to 0.15 mg·L-1.Detection limit (3s/k) found for the method was 2.8 μg·L-1.Those common co-existing ions were found not interfering to the determination of Mo(Ⅵ).Four kinds of bean samples were analyzed by the present method,giving values of recovery and RSD′s (n=6) in the ranges of 99.0%-103.5% and 0.74%-1.07% respectively.