Abstract: Cotton stalks were snapped and crushed to size of ca. 0.63 mm and hydrolyzed in H2SO4 (2.7+97.3) solution at 110 ℃ for 4 h. After cooling and centrifuging, the supernatant was taken and filtered on 0.45 μm filtering membrane. The filtrate was used for HPLC analysis for phenol and furfural, using Shim-pack VP-ODS C18 column and mobile phase of CH3OH-H2O (70+30) for separation and UV-detection with PDA detector at 272 nm for determination of both the phenol and furfural in the linearity ranges of 0.01 to 20.0 mg·L-1 and 0.01 to 30.0 mg·L-1 respectively. Detection limits (3S/N) found were same as 0.005 mg·L-1. Values of recovery found, by addition of standards at 3 concentration levels, were in the ranges of 90.6%-100.5% and 92.9%-99.8% with values of RSD′s (n=6) in the ranges of 1.1%-2.1% and 1.7%-2.5% for phenol and furfural respectively.