In order to detect the damage of the inner and outer walls of non-ferromagnetic metals, a medium and low frequency AC electromagnetic field detection model is designed. The coupling mechanism of magnetic flux leakage and eddy current effect in the detection of AC electromagnetic field is analyzed, and the electromagnetic detection device is made for experimental verification. Based on COMSOL finite element simulation, the two-dimensional simulation model is established. The simulation tests are carried out for surface defects and buried depth defects of different depth and sizes, and the relationship between voltage amplitude, phase of the coil and defect depth is obtained. Based on the simulation results, the electromagnetic detection device is made and the non-ferromagnetic metal test piece is tested. The results show that the manufactured electromagnetic detection device can penetrate the 18 mm stainless steel plate to detect a rectangular buried depth defect with a height of 5 mm and a length of 12 mm and a micro circular hole defect with a upper surface of 3 mm and Ф5 mm. It is concluded that the low frequency excitation signal has a good detection effect on the upper and lower surface defects of the test piece, while the intermediate frequency excitation signal is only suitable for the detection of upper surface defects.