Underground diaphragm wall joint and underground diaphragm wall construction method

The invention relates to an underground diaphragm wall joint and an underground diaphragm wall construction method. The underground diaphragm wall joint is used for connecting two adjacent unit wall sections and comprises an isolation plate and perforated plates; the isolation plate is used for being embedded between every two adjacent unit wall sections, the perforated plates are fixedly connected with the isolation plate, through holes are formed in the perforated plates at intervals, the perforated plates are used for being embedded into the unit wall sections, and the through holes are located in the unit wall sections; and at least two perforated plates are fixedly connected with the two faces of the isolation plate. The perforated plates and the unit walls on the two sides form a tight built-in occlusion effect, shearing force on vertical joints of the underground diaphragm wall can be borne, the adjacent unit walls form a whole to jointly bear vertical loads of an upper structure, and uneven settlement