According to the special feature of the how outside a char particle under forced convection conditions (Re < 150), a simplified model for calculating the burning rate of a char particle is presented in this paper. The burning processes of frontal and rear hemispheres are discussed, respectively. The effects of both flow and ash formation are considered in the study. Based on this model, a numerical simulation of the burning process is conducted for different type of char. Good agreement of the calculated results with corresponding experiment data demonstrates that this model is reasonable for the case with Re < 150.