During thermo-inductive inspection, an eddy current of high intensity is induced into the inspected material and the thermal response is detected using an infrared camera. Anomalies in the surface temperature during and after inductive heating correspond to inhomogeneities in the material. A finite element simulation of the surface crack detection process using active thermography with inductive heating has been developed. The simulation tool was tested and used for investigations on austenitic steel components with different longitudinal orientated cracks. The shape of the crack varies in the crack opening and the depth. The simulation model was based on the finite element programming software ANSYS. The suitability of the developed simulation of the inductive excited thermography for crack detection will be demonstrated by calculations and experiments. This paper focuses on longitudinal orientated cracks in austenitic steel, which are opened to the surface. The results show that depending on the shape of the crack the temperature distribution of the material under test made of austenitic steel is different. It will be shown how the crack size affects the temperature difference between the crack and the surrounding surface.