The invention discloses a track type large-span foldable and unfoldable machining robot. The robot comprises a track, a five-degree-of-freedom tail end posture adjusting device and a two-degree-of-freedom foldable and unfoldable mechanism; the two-degree-of-freedom foldable and unfoldable mechanism comprises a base, a first-stage parallelogram structure, a second-stage parallelogram structure, a middle triangular plate, a first driving assembly and a second driving assembly; and the first-stage parallelogram structure is installed on the base, and the two parallelogram structures are coupled through the middle triangular plate; the five-degree-of-freedom tail end posture adjusting device is connected with the second-stage parallelogram structure; and the base is movably arranged on the track in a matched mode. According to the track type large-span foldable and unfoldable machining robot, space wide-range moving and positioning of the five-degree-of-freedom tail end posture adjusting device can be realized, the robot can meet the requirement of a large-scale structural component for a large working space of machining equipment, the functions of wide-range positioning, local flexible posture adjustment and the like can be easily realized, and numerical control machining of the complex free-form surface of the large-scale structural component can be completed.