To develop a reliable monitor method for inspecting the quality and strength of the clinched steel and pre-strained aluminum joints, the electrical resistance method was introduced. A 0.7-mm thick galvanized SAE1004 steel and 1.0-mm thick pre-strained aluminum AA6111-T4 were clinched, and the section parameters, the electric resistance, and strength of the clinched joints were measured. The strengths of the clinched joints were evaluated and correlated with the bottom thickness and electrical resistance of the joints. The results showed that the pre-strained aluminum from pre-stamping significantly increased the electrical resistance (R) and decreased the variation of electrical resistance (ΔR) and strength of the clinched joint. Both the ΔR and bottom thickness can detect the strength variation for the clinched as-received and pre-strained aluminum-steel joints, but the ΔR was more sensitive than the bottom thickness to reflect the effect of aluminum pre-straining on the joint strength. Therefore, it may be more appropriate to use the variation of electrical resistance to inspect the strength of the clinched steel and aluminum joints.