Construction method for large ultra-deep well

The invention discloses a construction method for a large ultra-deep well. In the method, the well is constructed by a drainage method of combining a waterproof curtain and deep well point dewatering; the well is manufactured and sunk; when the well is sunk to a preset depth, the well is constructed by a no drainage method; and when the well is sunk in place, concrete is used for sealing a bottom underwater. The method is characterized by comprising the following construction steps: a, constructing the waterproof curtain by using a rotary jet grouting pile; b, performing deep well point dewatering construction; c, prefabricating the well by sections; d, sinking the well by using the drainage method; e, sinking the well by using the no drainage method; and f, sealing the bottom by using the concrete underwater. The construction method for the large ultra-deep well has the advantages that: the construction steps are designed scientifically and reasonably, the construction period is shortened, piping and quicksa