Construction layout of combined cavern group of underground nuclear power plant in depth direction of mountain

Disclosed is a construction layout of a combined cavern group of an underground nuclear power plant in a depth direction of a mountain. The construction layout comprises a nuclear reactor workshop cavern (1), two combined caverns, two electric workshop caverns (2), two pressure relief caverns (7), a first main traffic hole (8), a second main traffic hole (9) and a third main traffic hole (10), wherein the three main traffic holes are in communication with the earth surface; the nuclear reactor workshop cavern (1), the combined caverns, the electric workshop caverns (2) and the pressure relief caverns (7) form a nuclear island workshop cavern group; crown arch feet or crown end walls of each cavern of the nuclear island workshop cavern group are in communication with the earth surface through a top-layer cavern support system; and side wall bottoms of each cavern of the nuclear island workshop cavern group are in communication with the three main traffic holes through a bottom-layer cavern support system. The construction layout has short mileage, high security, convenient construction, better investment saving and high degree of modularization, and can be widely applied to the technical field of nuclear power engineering.