Abstract: This paper gives a set ofcalculating formula of the driving force moment that is responsible for the tube-insertself-rotating and automatical cleaning in heat transfer tubes, usingthe principle of momentum moment and kinematics. It can be usedto optimize the structure ofthe tube-insert with spiral flange. Based on the formula, severaltube-inserts of different structure are designed and compared throughexperiments. The optimal insert (No. D) can be used reliably at low flowingvelocity of more than 0.4m/s. The driving force moment and heat transfercoefficient are increased by 141\% and 50%, respectively. The flowresistance is in the limit of industrial standards.