The invention discloses a pipeline cleaning spray head supporting walking device adjustable in radial size. The pipeline cleaning spray head supporting walking device comprises a two-dimensional self-rotating spray head and a connecting pipe assembly. The two-dimensional self-rotating spray head is connected with the connecting pipe assembly through a pipe thread. A nozzle is arranged on the two-dimensional self-rotating spray head. Three sets of passive adjusting mechanisms are evenly distributed and mounted along the circumference of the connecting pipe assembly. Each passive adjusting mechanism comprises a passive supporting rod and a passive connecting rod, wherein the middle of the passive supporting rod and the middle of the passive connecting rod are hinged in a crossing manner. Fixed flanges and a fixed plate are arranged on the connecting pipe assembly. The connecting pipe assembly is sleeved with a fixed spring sliding block. The inner end of each passive supporting rod is hinged to the fixed plate, the inner end of each passive connecting rod is hinged to the fixed spring sliding block, and the outer ends of the passive supporting rods and the outer ends of the passive connecting rods are connected with active adjusting mechanisms correspondingly. Each active adjusting mechanism comprises a landing leg rod, a connecting block is hinged to the inner end of each landing leg rod, and adjusting pin shafts are arranged between each landing leg rod and the corresponding connecting block. Before use, for different pipe diameter sizes, the pipeline cleaning spray head supporting walking device can adapt to pipelines of different diameters through adjusting of the active adjusting mechanisms, and by means of the passive adjusting mechanisms, when meeting obstacles during use, the device can successfully cross over the obstacles in the manner of passively adjusting the radial size.