Abstract: The forming limit curves of three different strength grades of automotive beam steels were compared and studied, and combined with mechanical properties and microstructure, it was analyzed synthetically. The results show that with the increase of the strength grade, the elongation after breaking and strain hardening index of automobile beam steel decrease. The microstructure of the steels is mainly ferrite with a small amount of pearlite, in which ferrite is small and some of them have cluster aggregation characteristics. From the forming limit curve, it can be seen that the primary and secondary strain values decrease with the increase of the beam steel grade, and the main strain values at the extreme point（FLD0） of the main strain show the same trend.