The blades of gas turbine are usually long-term operated in harsh environments. Due to high temperature and pressure in operation, as well as many external impacts, blades may have various defects, such as erosion, distortion, wear, cracks and impact dents. In order to implement the remanufacturing of defective blade with laser direct material deposit (LDMD), cross-section curve (CSC) was reconstructed based on design characters and defect 3D model was extracted. First, the remanufacturing system structure of blade was given. Second, on the basis of CSC design characters, the positions of leading edge (LE), trailing edge (TE), suction side (SS) and pressure side (PS) were identified in cross-section point cloud. In order to obtain LE and TE, the circle curves were utilized to fit the data points with the deviation of point from the circle and fitting error as threshold values. Meanwhile, the cross-section point cloud was segmented. And under the constraint condition of tangency to LE and TE, a sixth degree polynomial function was selected to fit the SS and PS by using the least square method. After some whole CSCs were obtained, the perfect blade airfoil model can be achieved by lofting them. Sequentially, defect 3D model for LDMD was extracted in Boolean subtraction. At last, an application of blade remanufacturing was given, which proved that the method was feasible, and the future research direction was also proposed.