YG15 cemented carbides and 35CrMo steel were brazed with different content of element Ni in the article. The effect of the content of element Ni, brazing temperature and ultrasonic vibration on the mechanical properties and microstructure of the joints was investigated. It shows that continued α-Cu solution layers can be obtained by increasing the content of element Ni, and the shear strength peaked at 295 Mpa with the 4.7 wt.% Ni content filler metal at the brazing temperature of 800°C. It found that the brazing temperature influence the depleted zone width of element Co of joints through the impact on the diffusion of element Ni. The minimum of the depleted zone width of element Co is observed in the joints at the brazing temperature of 730°C, and the shear strength of the joints reached maximum 350 MPa. The brazing process with ultrasonic vibration can enlarge the width of the depleted zone of element Co of the joints, decrease the content of eutectic structure, and drive the WC particles migration into the bonds. The maximum shear strength of the joints with 17.5 μm depleted zone of element Co was obtained at 378 Mpa with ultrasonic brazing for 30s, increasing the shear strength of the joints by 6% than the joints without ultrasound.