Abstract: New negative Poisson's ratio crush box (NPRC) structure of vehicle front frame was presented. By studying the failure mode and plateau stress in plateau stage of cell, the mechanical properties of failure were discussed. It can be concluded that the NPRC structure shows better energy absorption capability than usual cellular structure with enhanced equivalent elastic modulus and plateau stress under in-plane loading. With mechanical analytical model of NPRC cell in plateau stage, the critical stress equations of elastic buckling and plastic collapse were developed, the conclusion that plastic collapse is the main failure mode of the structure is also presented. The parametric finite element model of NPRC cell by Matlab software was used to study the relationship between geometric parameters and plateau stress, which indicates that the plateau stress of cell is inversely proportional to length ratio and cell angle and in proportion to thickness ratio. And in-plane axial quasi static compressive experiment using 3×3 NPRC sample was carried out to verify finite element analysis results. The results conclude that the NPRC sample has equivalent negative Poisson's ratio (-11.97). The NPRC sample appears densification of cell and peak value of plateau stress increases with the increase of strain, which provides theoretical significance for improving energy absorption performance.