The utility model discloses a little inertia screwed pipe formula electro -magnet, the support mechanism comprises a guide sleeve, the yoke, the control coil, separate the magnetic ring, valve interface piece, the push rod with move the iron core, move the iron core, valve interface piece and control coil are installed in the yoke, it distributes around the axial wherein to move iron core and valve interface piece, the control coil is located the outside of moving iron core and valve interface piece, guide pin bushing and separate the magnetic ring and locate and move the iron core, between valve interface piece and the control coil, the push rod is connected on moving the iron core and is passed valve interface piece, the guide pin bushing includes anterior segment guide pin bushing and back end guide pin bushing, before the magnetic ring is located, between the back end guide pin bushing, it is porose along axial processing to move the iron core. The utility model discloses under the infrastructure, appearance and the dimension's that do not change existing proportion electro -magnet prerequisite, process the axial hole through adopting in moving the iron core, can reduce to move the quality of iron core to improve the linearity of proportion electro -magnet displacement - power characteristic, increase the working stroke of proportion electro -magnet.