Abstract: Addressing the problem of steel tube surface cracks as caused by the micro-alloying treatment with Element Nb,a manufacturing process with a chemical composition design free of addition of Nb for the BJ890 ultra-high strength seamless steel tube is worked out.Relevant experiment shows that when the heating temperature reaches up to 920℃,the BJ890 steel as treated with the non-Nb micro-alloying process has its austenite grain size enlarged.Accordingly the optimized heat treatment process scheme is prepared with which the steel tube as produced possesses comprehensive mechanical properties as up to relevant product requirements,and good low-temperature impact toughness at -40℃.