Abstract: There are deep overburdens, tens to hundreds of meters thick, on riverbeds in western China where many rockfill dams are under construction or will be built. A concrete cut-off wall is always constructed in the overburden beneath high rockfill dam to control the seepage through dam foundation, and a gallery is usually built to connect the cut-off wall with the earth or asphalt concrete core within the dam. Since the foundation gallery is under complicated condition, fracture and leakage are found in the galleries of some rockfill dams in operation, which endangers the safety of dams to a certain extent. In order to study the cracking laws and stress states of the foundation gallery, the monitoring data of several galleries of rockfill dams with earth or asphalt concrete cores are analyzed. One of the galleries is calculated by using the finite element method, and the dam construction and water impounding processes are simulated. The nonlinear elastic model is employed to simulate the concrete gallery. The laws of the stress states and the behaviors of structural joints of the gallery are obtained. The vulnerable parts of the gallery and some improvements of the reinforcement design for the gallery are suggested, which is helpful for similar projects.