Abstract：A preliminary conclusion is drawn that the reactivation of Maoping landslide is caused by the irrational coal mining in the Baiyan cliff to the east of the landslide. The conclusion is based on the monitored data from 1993 to 2000. In order to verify the above conclusion，a complementary monitoring program was implemented from July 2004 to January 2005，which includes the monitoring of rainfall，deformation by inclinometer，and water level in a borehole. Together with other monitored data，the further analysis was conducted on the hydrodynamic changes of the slide and their influences on deformation as follows：(1) hydrodynamic changes include two aspects：flow route change of Huang gully，which is resulted from coal mining-induced rock cracking and collapse of the cliff，and reservoir filling and operation；(2) the flow route change of Huang gully both raises the water table in the slide and keeps the high water table for a longer period；(3) as the water in Huang gully is completely from natural rainfall，so rainfall，especially intensive rainfall is the major factor leading to the acceleration of the slide deformation；and (4) after 1999，the influence of reservoir operation on the deformation of the secondary slide at the toe of the slide is weakened. As a landslide with the largest body and also the largest deformation in Geheyan reservoir，great attention should be paid to the instability by related authorities. Control measures should be considered first to intercept and drain the water from Huang gully.
