Abstract: A magnetic fluid sealed shaft assembly, a shielded motor, and a shielded pump, wherein the shaft assembly comprises: a housing provided with an accommodating cavity, the accommodating cavity being provided with a fixed structure on an inner wall; a rotating shaft supported and mounted in the accommodating cavity; a magnetic fluid sealing device which is located in the accommodating cavity and sleeves and is sealedly and fixedly mounted on the rotating shaft, wherein space is reserved in the housing for runout of the magnetic fluid sealing device following the rotating shaft and/or adjustment of a mounting angle and position; and a resilient member which is sealedly mounted on an outer sleeve of the magnetic fluid sealing device and sealedly connected to the fixed structure. This structure eliminates the additional axial force, radial force, external torsion, statically indeterminate force, etc., on the bearings in the magnetic fluid sealing device during operation.