The invention discloses a flexible active and passive knee-joint rehabilitation training device, comprising a linear drive unit, a leg bracket unit and a control unit, wherein, the linear drive unit comprises a baseboard, a rodless cylinder, a sliding table for the rodless cylinder, an inflatable extendible flexible driver, a guide rod, a spring, a fixed support, a connecting piece, a removable bracket and a sliding pair; the leg bracket unit comprises a thigh rod, a thigh supporting board, a shank rod, a shank supporting board, a feet bracket, a connecting rod, a T-type connecting piece, a L-type rod, a first regulating device and a second regulating device; and the control unit comprises an angular displacement sensor, a force sensor, a displacement sensor and a controller. The training device can conveniently achieve a plurality of rehabilitation training modes such as knee-joint passive training, active training and the like according to the rehabilitation degree of a patient, and an applying force (including a driving force in the passive training and a damping force in the active training) is regulated in a stepless manner.