The utility model discloses a tank top structure of a large low-temperature storage tank. The tank top structure comprises an outer tank top and an inner tank top, wherein the outer tank top is of a reticulated shell structure and comprises a reticulated shell and a skin; the inner tank top is of a suspended ceiling structure; the reticulated shell is a single-layer spherical reticulated shell, and the curvature radius is 0.8-1.2 times the diameter of the outer tank of the storage tank; the skin covers the outer surface of the reticulated shell; the inner tank top comprises a suspended ceiling plate and an annular connection plate arranged thereon; the annular connection plate is connected with the outer tank top through a hanging rod, so that the inner tank top is suspended at the lower part of the outer tank top; and the reticulated shell of the outer tank top is fixedly connected with the outer tank of the storage tank through a connecting piece, and the outer tank of the storage tank supports the tank top structure. According to the tank top structure disclosed by the utility model, the outer tank top is of an optimized single-layer spherical reticulated shell structure, the rod members are uniformly arranged, a small amount of steel is consumed, a great tank top load can be effectively borne, and the safety is high. An existing welding vertical flat-bottom cylindrical double-layer metal low-temperature liquid storage tank can be developed to a large one.