Boron is one of the most attractive additives of fuel used for ramjet engines, due to its high volumetric and gravimetric heating value. Studies focusing on the ignition and combustion model of a single boron particle have been taken place for a long time, the most outstanding model is proposed by the group of Kuo, which is simple and can be well used in CFD application. However, some drawbacks were found in this model, and a new model was proposed. In the new extended model, some physical processes of boron ignition and combustion were considered. At the ignition stage, the balance of (BO)(n) on the liquid oxide layer surface was considered. It was diffused from the boron-boron oxide interface, and then consumed by both the heterogeneous reactions and the evaporation of diboron dioxide on the surface. The evaporation process of boron oxide and reaction between water vapor and boron oxide were considered. At the combustion stage, the evaporation and boiling processes of boron were considered due to the high combustion temperature, some chemical reaction rates were adjusted. The influence of forced convection on the particle was considered in both ignition and combustion stage. A careful validation shows that the extended model is suitable for a single boron particle, especially at the combustion stage. Effects of gas temperature, gas pressure, oxygen mole fraction on boron ignition and combustion in ramjet engine were studied and could be useful for ramjet engine design. (C) 2017 Elsevier B.V. All rights reserved.