The present work deals with the fatigue strength and lifetime behaviour of a cast aluminium alloy AlMg4,5Mn0,7 which was produced by horizontal continuous casting process. The fatigue test was carried with Charpy-V-notch specimen wherein the material behaviour was examined depending on the orientation. For the portability of the results of the specimens, a model with Kirchhoff theory was created. The model of plate was performed using two methods of solution. On the one hand was created an analytical solution and other hand a numerical solution, wherein the results were compared. A finite element simulation using ABAQUS based on linear elastic materials data has been established, which were carried out for different clamping conditions calculations. For the life estimate has been performed a plate with a circular or elliptical hole, and based on the calculations and material testing a service life calculation with the fatigue software FEMFAT. For evaluating the fatigue life calculation, a test concept was conceived. The complete results of the fatigue analysis show a vibration strength values close to identical in the order of 27 N/mm2, independent of direction. This demonstrates isotropic behavior and homogeneity of the cast ingot. The comparative results of the numerical and analytical calculations on the cantilever (case 1) show an approximation of the analytic solution in which 2D model and a significant difference with the solution of the 3D model. In contrast, there are at both ends of the clamping plate (case 2). An approximation of the analytical solution with the 3D model and a difference with the solution of the 2D model. When clamping adjacent sides (case 3), the analytical solution with the solutions of the 2D and 3D model is almost identical.With regard to the tripartite clamped support case 4, the 3D model has the highest stress, followed the stress of the 2D model and the analytical solution. A reverse order of the results are obtained with total clamped support (Case 5). The lifetime calculation of the plates with the circular and elliptical hole model shows that the ellipse hole seems to habe no influence on the boundary conditions. So for the life assessment of plates with different holes, the local stress concept are proposed.