In high power laser system, the upstream flaw could induce light intensification in the downstream, thus damaging the optical component. In most of the research, the shape of the defect model is ideal, for example, Gaussian shape. However, the defect in the real system is non-ideal with different shapes. In this paper, the light intensification effect caused by defects with different shapes are compared by numerical simulation. Results show the shape dependence of downstream light intensification caused by flaws. When only the linear effect is considered, the change of defect shape could change the maximum light intensification factor and the downstream location for the maximum intensity. When the nonlinear effect is also considered, the light intensification effect will be more sensitive to the shape of defects. This research can provide some reference for the beam quality control and defect management in the high power laser systems.