The invention relates to a length-adjustable pull rod structure of a scaffold or formwork support, and aims to solve the problem that in a standard sleeve lock scaffold and a standard ring lock scaffold, the size of a pull rod of a steel pipe scaffold is unchanged, so that a mounting need cannot be satisfied when the reserved size of the pull rod of the scaffold changes. The scheme adopted by the invention lies in that the pull rod of the steel pipe scaffold comprises a fixed pull rod, a telescopic pull rod, a pull rod locking chuck and fastener linking wedges, wherein the fastener linking wedges are respectively fixed to one end of the fixed pull rod and one end of the telescopic pull rod, the pull rod locking chuck is fixedly arranged at the other end of the fixed pull rod, and the telescopic pull rod and the fixed pull rod form a telescopic movable inserting connection structure through the pull rod locking chuck. The pull rod structure disclosed by the invention has the beneficial technical effects of being simple in structure and convenient to use, the length of the pull rod can be adjusted discretionarily, and the building construction of the scaffold or formwork support is greatly convenient.