Abstract: According to the casting process of the engine piston, the types of defects that may occur on the surface of the piston combustion chamber are analyzed, and a detection method based on eddy current array technology is proposed. An eddy current array C-scan detection system for the piston combustion chamber was developed. Using two independently designed comparative test blocks, the effects of excitation frequency, high-pass filtering, detection speed and other parameters of the eddy current signal were studied. Then the inspection process was researched, and the process parameters were selected by comprehensively considering the factors such as inspection speed, depth, sensitivity and signal-to-noise ratio. Finally, the selected process parameters are used to adjust the impedance gain and phase. Under the condition that the detection velocity is less than 24 seconds per piece, the detection of artificial cracks of 5 mm×0. 12 mm×0. 2 mm (length×width×depth) on the surface of the piston combustion chamber is effectively achieved.