The invention relates to the field of construction of triaxial mixing piles, and in particular to a method for constructing a triaxial mixing pile in a water-rich sand layer. The method for constructing the triaxial mixing pile in the water-rich sand layer comprises the steps that stratum partitioning is carried out, specifically, according to the geological exploration data, the stratum partitioned along the height range of a triaxial mixing pile body; parameter setting is carried out, specifically, corresponding construction parameter values are set for each partitioned layer; parameter verification is carried out, specifically, through test pile coring, the pile-forming effect of each partitioned layer is verified, the stratum is layered and partitioned in the depth direction in advance, and the partitioned layers are obtained, so that in the construction process, the characteristic construction parameter values suitable for structural characteristics are selected when each partitioned layer is constructed, the pile-forming quality of each partitioned layer can be ensured, the amount of cement input in the entire construction process is reduced, cement waste is reduced, and theconstruction cost is saved while construction quality is ensured.