In the multi-layer and multi-pass welding of Inconel 690/321 stainless steel dissimilar metals,cracks,incomplete penetration,incomplete fusion and other defects may occur,accompanied by deterioration structure,resulting in the degradation of joint performance. In view of the above problems,the microstructure and properties of dissimilar metal welded joints are studied by means of metallographic structure analysis,chemical composition analysis and microhardness test.The results show that there is normal welding microstructure in each region and no obvious welding defects;there is TiC in degradation zone,the hardness of welded joint is generally low,but has good plasticity;in the multi-layer and multi-pass welding process,the tempering effect of the latter layer on the weld metal zone of the former layer improves the microstructure and the performance is not significantly affected.