Rear subframe of vehicle and vehicle

The rear auxiliary frame comprises a front cross beam, a rear cross beam and a longitudinal beam, the front cross beam and the rear cross beam are spaced in the first direction, the longitudinal beam is connected with the front cross beam and the rear cross beam, the front cross beam is a tubular beam and comprises a cross beam main body section and a cross beam reinforcing section, and the cross beam main body section and the cross beam reinforcing section are connected. The outer contour length size of the minimum cross section of the cross beam reinforcing section is larger than the outer contour length size of the maximum cross section of the cross beam body section. Through the arrangement of the cross beam reinforcing section, the strength of a weak area of the tubular beam is locally improved, and the risk that the tubular beam cracks due to the fact that local thinning is too large is reduced; the outer contour length size of the minimum cross section of the cross beam reinforcing section is larger th