Inconel alloy 690 is an austenitic nickel-based corrosion resistant alloy with about 30%Cr, which is considered as the most ideal steam generator tubing materials in nuclear power plants because of its superior resistance to intergranular attack (IGA). However, the existence of impurities and the addition of minor alloying elements cause significant difference of carbide morphology, microstructure and chromium depletion of Inconel alloy 690. In this work, the microstructure and grain boundary chemistry of Inconel alloy 690 with four different nitrogen contents have been investigated by SEM and TEM. Stacking fault probability (SFP) and IGA with respect to the microstructure was tested and analyzed. The results indicated that thermal treatment at 715 ℃ following solution annealing (SA) at 1080 ℃ caused a wide range of intergranular carbide morphology with the associated chromium depletion in the vicinity of grain boundaries. With the increasing of nitrogen content, the characters of the carbides ranged from thin continuous bands along boundaries to coarse discrete particles. Stacking fault probability was increased with the increasing of nitrogen content, and the value reached the peak at 100×10^-6 of nitrogen content, then it dropped. The corrosion tests showed that moderate nitrogen content alloy performed favorable intergranular attack correlated with the presence of semi-continuous grain boundary carbide and chromium depletion was mitigated. The consequent nitrides were appeared in high nitrogen alloy. So, about 100×10^-6 contents of nitrogen in alloy 690 is suitable by synthesis considering of carbides, nitrides and chromium depletion.