The numerical simulation has been carried out to investigate the effect of the center-body with of different equivalent widths (from 0.3 to 0.8,interval 0.05) in the trapped vortex combustor under four different inlet conditions,so as to select the width of the center-body in the trapped vortex combustor. The results show there is a proper scale of the width to establish the low velocity and steady flow region in the trapped vortex cavity. The total pressure loss at the combustor outlet increases with rising center-body width.