To address the medium to long-term deformation issues of underground diaphragm wall sheet pile wharf，we focus on the 100,000-ton-class curtain-type underground diaphragm wall sheet pile wharf project at Jingtang port area of Tangshan Port.Using prototype observation method,we investigate the medium to long-term deformation characteristics of the curtain-type underground diaphragm wall sheet pile structure during both the construction period and operational period,and obtain the structural deformation and anchor point displacement of the front diaphragm wall,curtain piles,and anchorage wall at different excavation stages and during operation period.The results demonstrate that the rate of change in horizontal displacement of the structure is greatest during the construction period of the curtain-type underground diaphragm wall sheet pile wharf structure dredged deep to near the design elevation.The cumulative horizontal displacement accounts for 80%-93%.The cumulative displacement of the anchor points accounts for 85%-91%.The dredging depth at the front of the wharf is highly sensitive to horizontal displacement,especially when it approaches the design value.The deformation stabilization time of the curtain-type underground diaphragm wall sheet pile wharf structure is approximately 7 years in the relied project.