The invention provides a down-hole 
impact high-pressure jet grouting composite 
pile forming method. The method comprises the steps of S1, 
pile hole forming, S2, high-pressure jet grouting 
pile forming and S3, precast pile sinking and specifically comprises the steps that a down-hole hammer is driven by high-pressure air to 
impact and 
drill a formed pile hole, meanwhile, an ejector 
nozzle of a down-the-hole 
impact high-pressure jet-grouting drilling 
machine ejects high-pressure jet-grouting 
cement slurry to 
cut, stir and reinforce soil around the pile to form a uniform 
cement-soil mixture, and then a pile hammering 
machine or a pile static pressing 
machine is adopted to drive a precast pile with the 
diameter smaller than the 
diameter of the formed hole of the down -hole hammer into the bottom of the hole along the center of the high-pressure jet-grouting pile, therefore a composite pile is formed; the pile forming method can be applied to the aspects of foundation treatment, pile foundations, foundation pit supporting, waterproof curtains, 
elimination or reduction of foundation 
liquefaction, expansion and shrinkage of 
expansive soil and the like, has the advantages that the quality is stable and reliable, construction is convenient, the construction period is shortened, materials and construction cost are saved, and the manufacturing cost is reduced.