Abstract: A AZ91 magnesium alloy vehicle steering control arm was used to prepare by casting-forging combined forming, the microstructure and mechanical properties of the control arm′s main force parts were studied and the tensile fracture was analyzed. The results show that the deformations were different in different zones of AZ91 magnesium alloy vehicle steering control arm after casting-forging forming, the obvious streamlined characteristics and dynamic recrystallization were found in large deformation zone, and the grains were fine equiaxed crystal. Compared with the die-casting, the tensile strength, yield strength, elongation and hardness of the alloy after casting-forging combined forming were 251.3 MPa, 156.9 MPa, 4.12% and 125 HV, respectively. The fracture mechanism changed from brittle fracture into ductile-brittle fracture.