The mechanical clinching process can be used for the load-bearing structures of thin-walled steel frame halls. Numerical simulation of crack propagation in a clinching joint using finite element method (FEM) software is an important tool for the analysis and prediction of the behavior of materials under load. This study focuses on clinch joints that must withstand high loads and repeated load cycles. Crack propagation in these joints can lead to failure of the entire structure, therefore it is important to understand the mechanisms of crack propagation and predict their behavior. Using specialized software, a numerical simulation of crack propagation was prepared, including modelling of joint geometry, definition of material properties and application of loads. The simulation provides valuable information on the crack propagation process, which allows optimization of the behavior of the whole structure and the reliability of the clinch joints.