The invention relates to an anti-interference magnetic powder flaw detector for outdoor use. The device comprises a platform, an annular plate, a cover plate, a controller, a magnetic powder box, a cleaning mechanism, a lifting mechanism, two magnetizers and four supporting legs, the lifting mechanism comprises a bottom plate, a supporting plate and two lifting assemblies, every lifting assembly comprises an orientation rod, a driving unit, a plurality of sliding rings and a plurality of first connecting rods, and the cleaning mechanism comprises a first motor, a first driving shaft, a turntable, a washing assembly, a drying assembly, a second motor, a second driving shaft, two translating assemblies and two fixing rods. The lifting mechanism drives a workpiece on the supporting plate to move to a closed interval formed by the annular plate and the cover plate to prevent the magnetic powder distribution from being affected by wind, so the device can run outdoors; and oil stains on thesurface of the workpiece are removed by the cleaning mechanism to prevent the magnetic powder distribution from being interfered, so a magnetic trace is correctly displayed, and the practicability ofthe device is improved.