The brazing of duplex stainless steels which is an essential process for rocket engine manufacturing has been investigated on bonding phenomena and shear strength. The UNS32550 was used for base metal, and the MBF-50 was used for insert metal. Brazing was carried out under the various conditions (brazing temperature : 1473K, 1498K, holding time : 0, 0.3, 0.9, 1.8 ks). There were various phases in the joint because of reaction between liquid insert metal and base metal, In the early stage, BN is formed in the bonded interlayer and base metal near the bonded layer. Cr nitride is formed in the bonded interlayer. The amount of BN and Cr nitride decrease with the increase of holding time. Superior shear strength of 550MPa is obtained by restraining the formation of nitride.