Underground diaphragm wall auxiliary construction structure and construction method

The invention relates to an underground diaphragm wall auxiliary construction structure and a construction method. The underground diaphragm wall auxiliary construction structure comprises a joint steel plate for separating a pre-constructed diaphragm wall groove section and a post-constructed diaphragm wall groove section; the joint steel plate comprises sealing plates arranged on the two sides, and joint pipes are arranged between the outer side faces of the sealing plates and the groove wall faces of the continuous wall groove sections constructed firstly. The outer arc face of the connector pipe is attached to the outer side face of the sealing plate, the outer arc face of the connector pipe is further attached to the groove wall face of the continuous wall groove section constructed in advance, and during construction, a reinforcement cage of the continuous wall groove section constructed in advance and the joint steel plate are hung into the continuous wall groove section constructed in advance; and the