The invention provides a continuous shearing and reciprocating reverse extrusion combined type machining device and method for preparing pipes. The continuous shearing and reciprocating reverse extrusion combined type machining device comprises an annular extrusion barrel, a variable-section extrusion core rod, an upper fixing pressing plate, a lower fixing pressing plate and a twisting type worktable, wherein the upper end of the annular extrusion barrel is connected with the upper fixing pressing plate, and the lower end of the annular extrusion barrel is connected with the lower fixing pressing plate; the variable-section extrusion core rod is arranged on the inner side of the annular extrusion barrel; a boss is arranged on the outer side surface of the variable-section extrusion core rod in a smooth transition mode; one end of the variable-section extrusion core rod penetrates out of a first through hole of the upper fixing pressing plate, and the other end of the variable-section extrusion core rod penetrates out of a second through hole of the lower fixing pressing plate, so that positioning of the variable-section extrusion core rod is realized; the lower fixing pressing plate is arranged on the twisting type worktable. The uniformity of the texture of pipes is improved by introducing the variable-section extrusion core rod and enabling the extrusion core rod to move relative to blank materials in the axial direction.