The invention discloses a double-gradient-strength passenger car stand column structure. The double-gradient-strength passenger car stand column structure is characterized by consisting of a longitudinal gradient strength stand column and a transverse filling gradient density foam material. As the transverse filling density foam material is bonded on the inner side wall of a gradient strength L-shaped plate in the length direction of the gradient strength L-shaped plate, the collision force of the key part-stand column of a passenger car closed loop structure can be guaranteed to be matched with the strength of the corresponding position in the passenger car tilting process, the stress of each surrounding part of a passenger car is more uniform, and the unloading of external impact load is facilitated. In addition, the transverse filling gradient density foam material enhances the rigidity of the stand column, and the energy absorption is more stable in the tilting of the passenger car, so that secondary collision casualties are reduced. Meanwhile, the foam material also achieves the effects of sound isolation and heat insulation, and improves the tilting safety and the comfort of the passenger car.