The invention discloses a scanning mechanism used for an optical remote sensing instrument. The scanning mechanism includes a scanning mirror assembly, a scanning mechanism support, a drive shaft assembly, a moving shaft assembly, a thin film support, a support light shade, a shaft light shade and a locking device protecting cover. The scanning mirror assembly includes a scanning mirror, a gluing bush, a flexible support and a scanning mirror support. The moving shaft assembly includes a moving half shaft, in-pair angular contact ball bearings, a switching flange, an electromagnetic locker, a bearing lock nut and a maze seal ring. The drive shaft assembly includes a drive half shaft, in-pair angular contact ball bearings, a bearing seat, a drive motor, a motor housing, a magnetic shielding shade, a round induction synchronizer, a synchronizer protection shade, a bearing locking nut and a maze seal ring. The scanning mechanism is advantaged in that the scanning rate is high and the efficiency is high; the scanning detection field is large; the scanning precision is high; the temperature adaptability is good; the structure is simple; the reliability is improved since direct drive is adopted and use of a speed reduction mechanism with a complex structure is avoided.