Abstract: The Songyue RCC dam is situated in the high cold region.The first-stage project is RCC gravity dam,and the second-stage project will adopt the attaching slope method to heighten and thicken the dam.The characteristics of the construction of RCC concrete in high cold areas are different from those in other regions.And the RCC dam heightening in cold regions has no available examples at home and abroad.So the key problems corresponding to the dam heightening must be studied deeply.On the basis of the practical situation of the Songyue project,the researches were carried out for the key problems such as the section design for the dam heightening,the material partition,the structural shape for the junction surface of the old and new concrete,thermal-stress analysis,and temperature control for preventing cracks.The study results will be applied in the Songyue dam heightening construction and would be helpful to other similar projects.