Parametric analysis of hot spot stresses is a complicated process for bird-beak Square Hollow Section (SHS) welded joints due to their characteristic configurations. This paper presents an efficient finite element modelling technique to simulate the hot spot stresses of diamond bird-beak joints. ANSYS Parametric Design Language (APDL) was used and the novel configurations including saddle and crown areas of bird-beak joints were mainly considered during the model establishing process. Tetrahedral-shaped solid elements were used so that the refined FE meshes satisfy the requirements of extrapolation regions that have been specified in IIW and CIDECT fatigue design guides. All procedures are automatically completed by pre-coded programs so that the parametric analysis and design formula fitting of Stress Concentration Factor (SCF) can be efficiently conducted. The accuracy of the FE models was validated by comparing with the existing experimental data.