The Automobile Body Structure Axial Collapse and Bending Stiffness Characteristics Exaction Method and Simplified Model for Automobile Side Impact are introduced in this article. The purpose is to reduce the modification time caused by immature design for the crashworthiness improvement. The side impact simulation tests that based on the established simplified model are carried out by LS-DYNA software. The simplified model is validated by the achieved result: Most of the error of intrusion distance nearby B-pillar is less than 13%. Side impact crashworthiness improvement with the application of the simplified model is proposed in this article and simulation work performed to verify the proposal is presented in this paper as well. Based on the results obtained, the intrusion distance of B-pillar and threshold in this improved model decreases by approximately 40% compared to the original model. Also the intrusion velocity of a critical point in B-pillar decreases by approximately 2.8m/s after improvement. The structural improvement at design stage becomes achievable by utilizing the effective simplified model.