The paper studied B-pillar crashworthiness in the car side impact by modifying CAD model of a domestic car. MDB is builded according to ECER95 regulation and a car side impact model is established finally. And the paper made simulation analysis and solve for the model based on HyperMesh and LS-DYNA. According to simulation analysis, focusing on the insufficient crashworthiness of B-Pillar two schemes were put forward: one was to change the B-pillar thickness; The other was to change the B-pillar materials.The results show that simply increase thickness is not feasible and changing the steel to aluminum alloy is feasible which greatly improved crashworthiness.