Abstract: According to machining technology and inner defect shape of 5A06 alloy forging spherical shell with thickness of 1.5mm, the nondestructive testing techniques and the testing difficulties of it were analyzed. After that, the reference specimens with simulated cracks of different sizes and delaminated defect were designed, at the same time, the special high sensitive probe was developed. By using optimized eddy testing parameters, it realized the effective testing to surface simulated crack defect with 5 mm×0.05 mm(Length×Depth) of the thin spherical shell, and it had high sensitive testing ability to 5 mm length line type defect and  0.5 mm planetype defect under about 1.0 mm penetrate depth. Then the testing method to products whole depth range was suggested.