Abstract: First derivative spectrophotometry was used in the determination of 5-hydroxyfurfual and furfural,which were produced in the hydrolysis of cellulose as intermediate products. After reacted with thiobarbituricacid solution,and by the method of zero-crossing measurement,5-hydroxyfurfural was determined at the wavelength 412 nm and furfural determined at 428 nm. Linear relationships between the values of 1st derivative,dA/dλ412 and dA/dλ428,and the concentrations of both the compounds were obtained in the range of 0.4-3.2 mg·L-1. Precision and recovery of the method were tested,giving values of RSD′s (n=7) 2.23% and 2.06%,values of recovery 96.0% and 105.0% for 5-hydroxyfurfural and furfural respectively.