The high protrusion on the clinched joint affects the appearance of the joint. A height-reducing method was investigated in the work to reduce the protrusion height. The clinched joint was produced with AL5052 sheet and AL6061 sheet. Flat dies were used to conduct the height-reducing process in the experiment. A rivet was used in the height-reducing process to control the material flow of the protrusion and increase the strength of the joint. The cross-tensile strength, tension-shearing strength and energy absorption were investigated in the study. The cross-tensile strength and tension-shearing strength of the joint can be increased by the height-reducing method. The neck thickness also can be enlarged with the reduction of the protrusion. The height-reduced joint can absorb more energy than the clinched joint in the failure process. The height-reducing method was effective for reducing the protrusion height and increasing the strength of the joint produced with different sheets.