The construction technology of underwater rising mortar concrete greatly reduces the engineering cost of temporary cofferdam, which makes it possible for the success and wide application of precast reinforced concrete caisson when building dock and terminal on the rock foundation. Combining with the project case of temporary water stop in the engineering of large docks, this paper analyzes the technical features, engineering methods and programs, construction points and quality control of temporary water stop construction of rising mortar concrete, and gives the instructive suggestions to the possible technological problems encountered in the rising mortar construction. The construction technology of underwater rising mortar concrete has its own unique construction methods and the construction characteristics of being economical, convenient, fast and safe, which can be extended in and applied to similar projects.