Ancient timber structures on sloped lands are an important part of the ancient Chinese architecture. Due to the unequal height constraint at the bottom of columns, they are different from the ancient timber structures on flat lands in the aspects of architecture layout, structure characteristics and seismic performance. In recent years, the investigations on seismic damage of ancient buildings show that the damage degree of ancient timber structures on sloped lands is generally more serious than that on flat lands. To protect ancient timber structures on sloped lands much better, the basic concept of ancient timber structures on sloped lands is expounded and the architecture characteristics,structure forms and structure characteristics of ancient timber structures on sloped lands are summarized. According to the results of many investigations on seismic damage of ancient buildings, the typical earthquake damage characteristics and causes of ancient timber structures on sloped lands are analyzed, such as foundation failure, column foot slip, mortise-tenon failure, column frame torsion, roof failure and frame collapse.The similarities and differences between seismic damage of the ancient timber structures on flat lands and those on sloped lands are pointed out.The key scientific problems of seismic research on ancient timber structures on sloped lands are illustrated from the aspects of dynamic characteristics, analysis model, seismic mechanism, failure mode and reinforcement method and the thinking and direction for the subsequent seismic performance research are pointed out.