The present disclosure relates to an upper limb assist system including a back bracket, an arm bracket, a motor, and driving belts, wherein the arm bracket includes an upper arm, a forearm, and a hand portion, two ends of the forearm are configured to be rotatably coupled to the upper arm and the hand portion respectively, the upper arm is configured to be rotatably coupled to the back bracket, the upper limb assist system further includes driving members and corresponding rotating wheels disposed on the upper arm, the forearm and the hand portion respectively, wherein the driving member is configured to have a first state and a second state.