Abstract: The biomass wastes, cotton stalk（CS） and wood sawdust（WS）, were pretreated by two different processes（dry torrefaction（DT） and hydrothermal treatment（HT）） and then densified to prepare biomass briquettes（B）. The physical properties and combustion characteristics of the resulted biomass briquettes were investigated. The results indicate that the bulk density and the compressive strength of the briquettes prepared from the dry-torrefied biomasses were reduced by0.03～16.7% and 23.2～61.0% respectively compared with the unpretreated briquettes. On the contrary, the bulk density and the compressive strength of the briquettes prepared from the biomasses hydrothermally pretreated at 230℃ and 200℃increased by 9.5 to 27.3% and 114.0 to 241.3%, respectively.Moreover, the calorific value of the briquettes prepared after the hydrothermal process increased by 5.1～59.0%. Compared with the untreated biomass briquettes, the combustion characteristics of the dry-torrefied biomass briquettes changed a little, while the maximum burning rates of the briquettes prepared from the biomasses hydrothermally pretreated at200℃ and 230℃ significantly increased. The calorific value of the briquettes prepared from hydrothermally pretreated at230 oC is 20.23～21.33 MJ/kg, while the maximum burning rate is 9.06～9.49%·min^-1, the comprehensive combustion characteristic index is 4.94～5.56 min~2℃~3, the bulk density is1152.5～1154.3 kg/m~3 and the compressive strength is 3.4～3.5 MPa respectively. In the research, the briquettes prepared from the biomasses hydrothermally pretreated at 230℃ are suitable for the use as domestic and industrial fuel because of the high heating value and the best combustion properties and physical properties.