In order to solve the difficulties in the forming process of high strength steel and find the most suitable forming process to meet its increasing market demand, for the high strength steel rectangular tube used in buses, its forming process and die were designed by software PROFIL, and the finite element simulation and tensile test were conducted. Then, the characteristics of two rolling processes, namely circle-to-rectangular forming(CRF) and flat-strip-to-rectangular forming(FRF) were analyzed in terms of elongation, dimension accuracy of hole diameter and residual stress, and the mechanical properties of angle and weld in FRF were mainly tested. Finally, the high strength steel rectangular tubes used in buses were obtained by the above two processes, and the elongation, dimension accuracy of hole diameter and residual stress were compared respectively. The results show that compared with CRF process, FRF process has obvious advantages in the forming of high strength steel rectangular tube, but the process still can be improved in the future.