Abstract: Taking typical butt joint as the research object, parametric modeling was carried out to establish the finite element model with the uncertainty of weld geometry, and the notch stress concentration coefficient Kt at the toe of butt joint was studied. Firstly, the influence of different types of cells and mesh size on Kt is explored, and the element size and type are given through finite element mesh sensitivity analysis. The joint stress was extracted from the butt joint forward, and the stress distribution map was drawn to obtain the maximum stress concentration position at the weld toe. Then, by introducing control points to describe the changes of weld geometry, the uncertainty of weld geometry is truly reflected. Combining with the distribution law of actual measured weld shape data, a large number of weld geometry parameter data are obtained by random sampling. Finally, Kt is calculated based on notch stress method, and the statistical analysis is carried out to explore the distribution law of Kt when the butt joint geometric parameters of the weld are uncertain. The results show that the distribution meets the normal distribution.