A passively balanced load-adaptive upper limb exoskeleton. An upper arm (A), an elbow (B), a forearm (C), and a hand (D) are arranged sequentially from left to right. An upper arm upper rod (A1) and an upper arm lower rod (A2) each are hinge-connected to an upper arm elbow housing via a bearing. A forearm upper rod (C1) and a forearm lower rod (C2) each are hinge-connected to a forearm elbow housing via a bearing. An upper arm support rod (E) is disposed between an upper arm driving mechanism (A4) and an upper arm elbow assembly (B1). One end of the upper arm support rod is fixedly connected to two upper arm support rod slide blocks (9) in the upper arm driving mechanism, and the other end thereof is hinge-connected to protruding shafts on two sides of an upper arm lead screw nut connection member via bearings. A forearm-upper arm support rod is disposed between a forearm driving mechanism (C4) and a forearm elbow assembly (B2). One end of the forearm-upper arm support rod (K) is fixedly connected to two upper arm support rod slide blocks in the forearm driving mechanism, and the other end thereof is hinge-connected to protruding shafts on two sides of a forearm lead screw nut connection member via bearings. The hand is hinge-connected to a wrist. The upper limb exoskeleton of the invention is used to facilitate handling of heavy goods or carrying of certain items.