Abstract: The effects of heating rate and particle size on degradation of polyethylene to oils in supercritical water were investigated with a 125mL autoclave. The results show that with the increase of heating rate, the yield of oil increases and that of gas decreases. In addition, the fraction of heavy hydrocarbons and the ratio of 1alkene to n-alkane are relatively high under higher heating rate. More gas products and alkenes are produced using small particle polyethylene as raw material.