The invention discloses a caliber self-adjustable 3D (Three Dimensional) printer spraying nozzle. The caliber self-adjustable 3D printer spraying nozzle comprises a spraying nozzle which is fixedly arranged, wherein the spraying nozzle comprises a material guide pipe for conveying consumable items and the spraying nozzle and the material guide pipe are arranged on the same axis; the material guide pipe is in sliding sleeve joint with a material storage pipe and can move along the self-axis of the material guide pipe; the spraying nozzle further comprises an extruding opening outer wall and a flow control body; and the flow control body and an inner wall of the extruding opening outer wall can be switched between a matching state and a releasing state along changes of an extruding amount. According to the caliber self-adjustable 3D printer spraying nozzle, self-adaptive adjustment of a caliber range is carried out according to a flow speed and a flow of the consumable items, and the control precision is high; and the time for printing an object with relatively low precision by a 3D printer can be remarkably shortened.