Directional repair of the same material by laser direct forming is performed on the columnar crystal substrate of DZ125L. Microstructure and normal mechanical properties of cladding layers are analyzed and tested. Besides, the mechanical properties of the interface between cladding layers and directional substrate are tested. The results show that the microstructure of laser direct forming DZ125L is columnar crystal with the primary dendrite arm spacing of 8~12 mm and the deterioration of secondary dendrite arm. The size of columnar crystal after heat treatment rises to 30~90 mm and γ′ strengthening phases separate out on the matrixes of columnar crystals in quantity and uniformly; The longitudinal tensile strength of as-deposited columnar crystal is 1312 MPa, while the elongation is 5.27%. After heat treatment, the longitudinal tensile strength and elongation are 1201 MPa and 6.69%, respectively, which both meet the national standards. The interface between cladding layers and directional substrate shows good mechanical property, which can meet the operation requirements.