The invention relates to the field of engineering construction, in particular to a large deep foundation pit construction method under the complex condition. By applying the large deep foundation pitconstruction method under the complex condition, construction of an urban underground space foundation pit can be quickly completed, the foundation pit is effectively held up and supported through enclosing piles, a soil nailing wall, a supporting structure, a prestree anchor cable, a between-pile sprayed concrete net and the like, and the stability of a foundation structure is ensured; and according to the large deep foundation pit construction method, multi-layer progressive cycle excavation is achieved, the construction speed is high, supporting is stable, the large deep foundation pit construction method is suitable for transfer sites for multi-line subway intersection with the large construction area and high environmental sensitivity, and the effect is good.