Abstract: Transformation-difliasion brazing is method combining trans formation superplastic diffusion bonding with diffusion brazing.Thebrazing method offers advantages as follows:the numbers of thermal cyclecan be reduced;the tiffusion efficiency can be raised;the microstructure of HAZ can be improved.In order to clarify the defects and interface mi-crograph in transformation-diffusion brazed joints,the joint was examined by SEM and EDS.The results are as follows:a sound bonded inter-face is obtained without sheet inclusion,pore and unbonding.And the characteristics of the defects in the joint are as follows:the defects existsin the residual interlayer apart from the bonded interface;it is not inclusion but cavity;the size of cavity is much smaller than that of grain;the cavities exist sparsely and random.It is suggested that the cavities are CO pores which are caused by carbon reduction.