With the rapid development of lightweight automobiles, the clinching joint technology of ultra-high-strength steel with aluminum alloy sheets have been paid more and more attention. However, due to significant differences in plastic deformation capabilities between the two metals, particularly the difficulty of steel sheet deformation, conventional clinching processes often result in insufficient joint interlocking or fracture issues. Although the preliminary use of clinching processes with preforming methods has shown some effectiveness in connecting two types of sheets, the bond strength is not high. This study employs finite element simulation and orthogonal optimization methods to investigate the impact of relevant process parameters on joint morphology in clinching processes with preforming. Under the condition of optimizing process parameters, a clinching punch with an added pressure-step structure was proposed to compact the joint and further enhance joint quality. Experimental verification demonstrates the feasibility of the improved clinching processes with preforming for bonding ultra-high-strength steel and aluminum alloy sheets.