The invention relates to a structure and construction method of a middle sea mine shield joining tunnel overlapping type joint, and belongs to the technical field of urban rail transit engineering design and construction. Normal mine law section, shield machine receiving section, box body transition section, shield reinforcement section and normal shield section are sequentially communicated to form a gradient stiffness joint structure. The mine shield joining tunnel overlapping type gradient stiffness joint structure adopts concrete initial support spraying, reinforced concrete segment prefabricating, a chassis steel structure, cast-in-place concrete multiple lining and grouting multiple overlapping segments to form stiffness gradient; the overlapping type joint length is long, a multi-layer structure is grouted several times, and the waterproof effect is good; the construction method is simple in process and convenient to operate; using the mold-built reinforced concrete box body and multiple strengthening structures, the construction risk is small and the joint is safe and reliable.