Abstract: Although the Q460D steel is widely used for plate-making,it’s very difficult to make the seamless tube with this type of steel. Nevertheless,a hi-strength and hi-toughness large-sized heavy-wall structure-purposed seamless tube in Q460D steel is successfully developed by means of optimizing the steel’s chemical composition,and adopting proper heat treatment process. Relevant mechanical properties of the tube are as follows. After being normalized,its yield strength is ≥440 MPa;tensile strength ≥550 MPa,and longitudinal elongation ≥17%. And the impact test as made at -20 ℃ to the tube shows that the average longitudinal impact value is ≥80 J,and the average transversal impact value ≥60 J. All the above property test-resulting data are in compliance with relevant customer requirements.