The invention discloses a fuel storage tank for nuclear power plant spent fuel dry-type storage. The fuel storage tank comprises a storage tank body and a storage tank support structure fixed at the periphery of the storage tank body. The storage tank body comprises a cylinder, an outer top cover, an inner top cover, a flange and a base plate. The base plate is fixedly connected at the bottom of the cylinder. The flange is fixedly connected at the top of the cylinder. The top of the flange is equipped with a step sealing surface. The inner top cover and the outer top cover are connected with different steps of the step sealing surface of the flange through bolts. Compared with the prior art, the fuel storage tank employs a flange-type top cover structure, thus the fuel storage tank top cover sealing performance is ensured, and the sealing operation difficulty is lowered. A spent fuel assembly can be loaded and taken out and recycle of the fuel storage tank can be achieved.