The effect of subcritical water (SCW) pretreatment on cellulose recovery of water hyacinth was investi- gated in this study. Before SCW treatment, cellulose and hemicellulose contents of dried water hyacinth sample were 25.0% and 11.0%, respectively. After being treated at 165 °C and 50 bar for 30 min with a water to dried sample ratio of 10:1 (ml/g), cellulose content in the treated sample was 68.2% which is 131.5% of the untreated sample. Pretreatment using H 2 SO 4 was also carried out in order to understand the effect of the chemical on lignocellulose degradation and compare it with that of SCW pretreatment. The results revealed that SCW treatment was an environmentally friendly method to recovery cellulose and remove lignin from water hyacinth which is promising for bioethanol production. The effects of SCW treatment on the composition and structure of water hyacinth were studied by TGA, FTIR and SEM.