Abstract: In order to get the maximum stress in the transverse part of the three-edge fillet weld bearing concentrated load, the rectangle steel board was divided into three regions with triangle, and equivalent force and deformation models were constructed using fixed support and straight bars with constant cross section. Based on the deformation compatibility condition, force equilibrium equations at the point of load were presented and the axial force in bar was given. Then, the analytic solution of maximum stress in the transverse weld was derived. The results given by the prediction model are in good agreement with that of finite element simulation when the length-width ratio is greater than or equal to 1 but less than or equal to 10. It shows the prediction model proposed in this paper is valid.