The uneven deformation can decrease formability of Tailor Welded Blanks (TWB).The integrated strength is a key factor that determines the uneven deformation besides the technological conditions. In this paper, the influences of integrated strength on cracking trend and cracking type are investigated through bulging simulation and experiments. It is proposed that the integrated strength should be considered as a crucial factor during the TWB designing. Reasonable integrated strengths matching of base metals can improve the formability of the tailor welded blanks and reduce the trend of cracking. In the case that the integrated strengths of base metals are significantly different, the cracking occurs in the weaker side and is parallel to the welded seam; while the cracking appears in the welded seam and is vertical to it under the condition that the integrated strengths match well. The corresponding technological measures can be adopted as the guidance for materials selection and reasonable matching in the designing.