In ship-lock engineering,the surface steel plate of a novel steel-faced concrete composite structure is exposed to the environment and subjected to cyclic thermal loads,which may cause non-uniform long-term structural deformation and further lead to interfacial voiding failure of the structure.This study conducts an in-situ prototype observation test on thermal stress at a large ship-lock project，aiming to investigate the temperature-field distribution and structural strain response of steel-faced concrete structures under periodic thermal stress.Temperature sensors are arranged along the depth gradient inside the steel-faced structure to obtain the temperature field distribution of the structure,and two types of strain sensors are installed on the steel surface and embedded inside concrete respectively to acquire strain response data of the composite structure under periodic thermal loads.The results show that under high-temperature weather on sunny days,the temperature difference between the steel-faced plate and the concrete can reach 14 ℃,while the interfacial strain difference can exceed 30×10-6,and periodic cyclic thermal stress forms on the steel plate surface.It indicates that thermal stress is a vital factor affecting the long-term stability of steel-faced concrete composite structures for ship locks,and the structure faces risks such as interfacial voiding and fatigue failure under cyclic thermal loads.