Abstract: Objective The aim is to investigate influence of different brazing gaps and post-weld heat treatment states on the microstructure and properties of DD26 alloy and CoCrNb alloy brazed joints, and provide analytical support for the application of CoCrNb wear-resistant alloy in aero-engine components. Methods A nickel-based brazing filler metal (B-Ni55NbCoWCrAlSiMo) is utilized for brazing the DD26 alloy and CoCrNb wear-resistant alloy in vacuum. The microstructure and properties of the brazed joints with three brazing gaps under different post-brazing heat treatment conditions are analyzed. Results The results indicate that, after aging heat treatment, the microstructure of brazing seam with 0.05 mm gap forms a continuous precipitation phase band riching in W and Cr elements at the interface with the base material of DD26 alloy, and rupture life under the conditions of 1050 ℃/25 MPa is reduction. The brazing seams with different gaps are primarily composed of γ matrix, γ/γ′ eutectic structure and precipitation phase riching in Cr, W and Nb elements. With brazing gap increasing, the brittle boride phase in the brazing seam increases, transitioning from strip-like to coarse skeletal shape. The rupture life of brazed joints with 0.05 mm and 0.10 mm gap at the condition of 1050 ℃/25 MPa do not show significant discrepancy, maximum both exceed 120 h. The rupture life of the brazed joint with 0.15 mm gap at the condition of 1050 ℃/25 MPa increases, maximum reaches 159.67 h. Conclusion The B-Ni55NbCoWCrAlSiMo brazing filler metal can achieve great brazing of DD26 alloy and CoCrNb wear-resistant alloy. The brazed joint with 0.15 mm gap exhibits outstanding rupture property. During joint failure, cracks initiate at brittle precipitation phases near the DD26 alloy side, then propagate along these precipitation phases leading to fracture.