The invention provides a precise compact type 3D printer powder supply mechanism and a transmission method. The precise compact type 3D printer powder supply mechanism comprises a lower cylinder body, a spline assembly, a lead screw and a motor, wherein a supporting part is arranged above the lower cylinder body, the spline assembly comprises a spline shaft and a spline sleeve, the spline sleeve is fixed to the bottom surface of the supporting part, the spline shaft can be inserted into the spline sleeve in an axial motion mode, and one end of the spline shaft extends out of the lower cylinder body. The lead screw comprises a screw rod and a lead screw nut, wherein the lead screw nut is arranged in the lower cylinder body and is fixed to the bottom end of the spline shaft, the screw rod is in threaded connection with the lead screw nut and extends into the spline shaft, and the screw rod is connected with the servo motor. The powder supply mechanism has high linear motion precision through connection and transmission between the lead screw and the spline assembly and meets the transmission precision demand of a 3D printer. In addition, the screw rod extends into the spline assembly, and the powder supply mechanism has the advantage that an arrangement space of a transmission structure is small.