The invention provides a method for constructing the circular deep foundation support, comprising the following steps that: firstly, a circular pool wall I (6) is constructed by a segment topdown construction method, wherein, the first segment of the circular pool wall I constructed by the segment topdown construction method is taken as a supporting ring beam, after the digging depth is up to the needed degree, a lower cushion coat (9) and base plate (8) of the pool base plate are cast with concrete, and the pool wall II (7) of the remaining part is constructed by the regular construction method upwards from the base plate (8). Compared with the prior art, the method has the characteristics that the construction degree of advancement is rapid, the cost is low, the deformation is easy to control, the engineering quality is good, the foundation ditch has a high degree of safety, and the method is applicable to circular foundation ditches with any digging depths.