Normative system design of ?76mm steel tooth tricone bit was carried out， aiming at the small diameter non-coring drill. The paper designed the value of the structure parameters and checked the calculated diameter of ?76mm steel tooth tricone bit， referring to the value of structure design parameters of domestic petroleum tricone bits. The drawing method of crushing-diagram at the drilling-hole bottom and gear ring meshing-diagram， as well as the optimization method for the tooth ring arrangement of milling tooth cone are introduced systematically. Using steel ball to lock cone， with the unsealed sliding bearing structure. And the ball bearings are designed and calculated， to determine the number of balls， rolling track size， and clearance. The parameters of wedge teeth are calculated accurately， to determine the angles and installation angles of the milling cutters. The part details and processing technology of small diameter steel tooth tricone bit are described. The problems of the traditional heavy manual calculation and cumbersome 2D projection manual drawing have been solved， by utilizing Excel functions and 3D parameterized solid simulation software， improving the design efficiency and accuracy， to provide a reference for the design of similar roller cone bit.