The invention discloses a large open caisson construction method for a building concentration area. The large open caisson construction method is characterized in that a row of drilling protective piles is firstly constructed around an open caisson, and safety of surrounding buildings is ensured and side friction resistance of a well wall is reduced to facilitate subsidence; excavation and replacement filling are performed on an open caisson foundation; after replacement filling and compactness are performed, foundation bearing capacity meets requirements, and steel shell open caisson assembly is performed; layered height addition is performed on a concrete open caisson; caisson sinking is performed in a combined mechanical soil-excavation mode of an excavator, a gantry crane and a crawler crane according the principle of positioning accurately, firstly performing in middle and then performing at sides, performing symmetrical layered soil sampling and keeping proper depth. The large open caisson construction method disclosed by the invention solves the problem about how to ensure large open caisson construction quality of the building concentration area and safety of buildings around the large open caisson, and improves construction efficiency and reduces construction cost while ensuring open caisson construction quality and safety of the buildings around.