The optimum technology and reaction kinetics of toluene oxidation to benzaldehyde in supercritical carbon dioxide and subcritical water without catalyst were studied.The experimental results showed that the oxidation in supercritical carbon dioxide was a zero order reaction with activation energy 50.9 kJ8226;mol-1 and the oxidation in subcritical water was a consecutive reaction consisting of two first order reactions with activation energy 89 kJ8226;mol-1 and 76 kJ8226;mol-1 respectively.The optimum conditions for supercritical carbon dioxide were:P=25 MPa，T=180 ℃，t=4 h，η=2.5 and those for subcritical water were:P>P0，T=350 ℃，t=1 h，η=3.5.