Abstract: Effect of different heat treatment on grain boundary character distribution of 1Cr18Ni9 stainless steel was investigated by EBSD. The results showed that,in hot rolled specimen the low CSL grain boundary was about 85% and mainly locate at Σ3,Σ9,Σ27,Σ29;the grain boundary character distribution varied after heat treatment ,in water cooling specimen the low CSL grain boundary mainly located at Σ3 and Σ9 with Σ3 as much as 90%,in deep cooling specimen the number of Σ3 was even more,above 95%. The GBCD of specimens for water cooling and deep cooling was much similar,but its distribution were different,in water cooling specimen the low CSL mainly located at high angle boundaries but the CSL did not form a network;in deep cooling specimen the low CSL were distributed in the network of general high angle boundaries and formed a network of special boundaries which could cut off the connections in general high angle boundaries.