The fast devolatilization of biomass is the first step of thermochemical conversion in fluidized bed boilers or gasifiers. Some advanced devolatilization models applicable to a wide range of biomasses and process conditions have been developed on the basis of a detailed description of the physico-chemical mechanisms and of biomass standard analysis. In this study, the results of a biomass devolatilization model taking into account the main physical and chemical phenomena are reported. Attention is focused on biomass thermal properties derived from its composition and density. The kinetic scheme is based on the lumped kinetic model of (Ranzi et al., 2008) and its further development. Predictions of the complete devolatilization time of biomass thick particles are compared with experimental results obtained in different high-temperature fluidized bed reactors. Experimental results obtained with biomass pellets under image furnace conditions are also used to assess the dynamic release of volatile matter predicted in transient state. The great interest of predictive model able to reduce the number of input parameters for any biomass type is finally underlined.