The invention discloses a middle-opened type anti-freezing device for an LNG immersed pump pool. The device comprises a protective shell spliced by shell assemblies symmetric left and right. The protective shell is connected with a flange cover through a flange ledge, wherein the flange cover is spliced through two flange cover assemblies. An insulation layer spliced by two insulation layer assemblies is arranged on the inner side of the protective shell. Each insulation layer assembly is internally provided with a set of LNG guide pipes. An oppositely-opened insulation packing layer is arranged at the top of an LNG immersed pump. An oppositely-opened liquid inflow joint is arranged at the lower portion of the protective shell. An oppositely-opened liquid outflow joint and an instrument pipeline joint are arranged at the top of the flange cover. By the adoption of the device, cooling capacity of a diffusion pipeline of an LNG station device can be fully used, the cold loss of the pipeline and the LNG immersed pump is reduced, and the LNG immersed pump is prevented from being frozen. A middle-opened type structure is adopted, the shell can be machined and assembled on the site, and the anti-freezing device has the beneficial effects of being compact in structure, high in universality and the like.