Flexible gear and harmonic reducer with same

The utility model provides a flexible gear and a harmonic reducer with the flexible gear. The flexible gear is of a cylindrical structure and comprises a transmission part. The inner circumferential wall of the transmission part is of a segmented structure in the axial direction of the transmission part, the segmented structure at least comprises a first shaft section, a second shaft section and a third shaft section which are connected in sequence, and the average wall thickness of the transmission part at the second shaft section is larger than the average wall thickness of the transmission part at the first shaft section and the average wall thickness of the transmission part at the third shaft section; outer teeth are formed on the outer peripheral wall of the transmission part; the first shaft section and the third shaft section are both of an unequal-inner-diameter structure, the second shaft section is of an equal-inner-diameter structure, the inner diameter of the first shaft section is gradually redu