The invention discloses a construction method of a river-crossing open-excavation deep foundation pit. By adopting the construction method of the river-crossing open-excavation deep foundation pit, construction of city underground space foundation pit of open-excavation river-crossing can be rapidly completed, enclosing piles, anti-pull piles, concrete support, steel support and shotcrete nets between piles are adopted to form effective support for the foundation pit, the stability of a foundation pit structure is ensured, the construction method of the open-excavation deep foundation pit crossing the river is constructed front and back with intervals, multilayer progressive circulating construction of each interval is carried out, the construction speed is high, the support is stable, theconstruction method of the open-excavation deep foundation pit crossing the river is suitable for subway line open-excavation river-crossing construction with larger construction area and high environmental sensitivity, and the effect is good.