The invention relates to an anchor rod construction method in a drilling, spraying and infusing integrated enlargement body; a single-pipe drilling, spraying and infusing aiguille equipped with a hydraulic controllable on-off auxiliary grouting hole and a long drillrig anchor rod driller which can implement the single-pipe high-speed spraying jet cutting technique are adopted to drill holes; whenthe drilled hole reaches a set depth, the aiguille is moved to a set position of an anchor root hole section; high-pressure clear water or grout is conveyed to the aiguille to produce a high-speed spraying jet cutting anchor hole sidewall and form an anchor root hole meeting the design need; after the operation of the anchor root hole enlargement is completed, the aiguille is lowered to the bottom of the anchor hole, then the aiguille is slowly retreated and the grout is continuously infused by the auxiliary grouting hole till the grouting of the anchor hole or the grouting replacement of theanchor hole is completed, then an anchorage cable body is lowered to the anchor hole with filled grouts to form the anchor rod of the enlargement body. The aim of the invention is to provide an anchor rod construction method in the drilling, spraying and infusing integrated enlargement body, which has high bearing capacity of the anchor rod, good durability, less construction equipment, simple technology, high efficiency, low cost and no pollution, and can carry out construction operation under the conditions of various stratums.