In order to solve the problems of short construction period, large engineering quantity and high construction requirements of the upstream cofferdam for the Julius Nyerere Hydropower Station in Africa after the river closure, a high-efficiency filling technology for composite cofferdam is proposed. Five efficient filling construction processes and key technologies have been focused, including bottom water-rushing concrete pouring, rockfill concrete pouring on the left bank, downstream prefabricated block formwork construction, upstream clay impermeable layer leveling construction, and main cementitious sand and gravel metamorphosis rolling construction. Engineering practice shows that the new high-efficiency filling technology for composite cofferdam can greatly optimize the construction organization and efficiency, and finally completes the safe, efficient and high-quality construction of the cofferdam before the flood season arrives.