Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${Delta}P-N_f$ curve were systematically rearranged in the $Deltasigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $Deltasigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.