Abstract: A new algorithm for defect detection based on weak magnetic detection technology is presented to detect crack defects at the edge of turbine blade of aeroengine effectively. The feasibility of the detection technology on determining the edge crack defects in the turbine blades was theoretically evaluated. And in order to minimize the lift-off height, we designed the scanning tooling and conducted the weak magnetic detection on the artificially engraved turbine blades in the geomagnetic environment. With combining the magnetic gradient method and the extreme value methods, data processing is performed on the original signal to extract abnormal signals. The results show that the magnetic induction intensity signal at the crack has obvious changes, and the defect detection position error is less than 2.5 mm. The combination of magnetic gradient method and extreme value method can reduce noise interference, increase the signal-to-noise ratio, and amplify the defect signal. When the crack depth ranges from 0.2 to 0.4 mm, the intensity magnetic induction signal increases with the crack depth. Therefore, the proposed method is available for the flaw detection in turbine blades with a depth of less than 0.4 mm, and corresponding signal identification is obvious.