Abstract: The effect of Mo on the susceptibility to SCC of the low alloy steels in nitrate solutions has been studied by SSRT technique on the background of the intergranular stress corrosion cracking at high temperature.The addition of Mo to the alloy steel is favorable for the transformation of ferrite to bainite and/or pearlite and the latters are more resistant to SCC than the former.The diagram of "temperature-Mo content-SCC" of the system "low alloy steels/nitrate solutions" is proposed.