Abstract: Stress distribution and development of vertical, horizontal and toroidal fillet welds under different levels of uniaxial tension has been obtained by nonlinear finite element method. From this analysis, the force distribution and development of the three different direction welds were clarified, and the relation between the height-width ratio of stiffener and the vertical weld’s stress level was pointed out. The more rigorous calculation formula of fillet weld based on the results of numerical analysis was proposed. At last, the reasonability of the proposed formula was verified through static experiments of rigid flange joint. The comparison between finite element analyses and experiments shows that the normal stress of vertical fillet weld presents an asymmetric distribution with larger stress occurring at the top and smaller stress occurring at the bottom, and the boundary of tension and compression locates at the height of 1/5; stress concentration occurs at both ends of fillet weld; the structural safety is guaranteed in consideration of partial plasticization; the proposed formula for fillet weld can be applied in practical engineering.