Abstract: Under the simulated physiological conditions,by the interaction of serum albumin and cyanoethyl uracil (CEU),an intermediate of nucleoside drugs,an extraordinary change of inherent fluorescence of serum albumin was observed;and linear relationship between the magnitude of synchronous fluorescence intensity and concentration of serum albumin in the solution was obtained.Based on these facts,a new method of synchronous fluorimetric determination of human serum albumin (HSA) and bovine serum albumin (BSA),using CEU as probe was proposed.Ranges of linearity for HSA and BSA were found to be 1.38-496.2 mg·L-1 and 1.56-624.0 mg·L-1,with values of detection limit (3S) 0.045 mg·L-1 and 0.051 mg·L-1,respectively.The proposed method was applied to the determination of HSA in human serum sample and BSA in bovine serum sample,and on the base of these samples,standard solutions of HSA and BSA were added to test for recovery of the method.Values of recovery and RSD′s (n=6) found were in the ranges of 95.1%-102.5% and 0.43%-2.72% respectively.