Abstract: The seamless steel tube in the dual phase steel containing ferrite and martensite as base structure is developed by means of getting the hot-rolled Q345B seamless steel tube with initial structure composed of ferrite and pearlite processed with the medium-frequency induction heat treatment. And then,the dual phase steel tube is further subjected to the circular processing to get ultra-fine grain base structure of it. Described here are the major aspects of the said medium-frequency induction heat treatment process for the dual phase steel tube,including the process de- sign,testing of the heat treatment process and the result. The research result leads to the conclusion that it is quite practical to use the medium-frequency induction quench process for developing the seamless dual phase steel tube.