The invention discloses a method for infield transporting and unloading of spent fuel in a nuclear power plant. The method comprises the following steps: S1, transporting a spent fuel loaded transportation container to an unloading area in a horizontal state; S2, placing the transportation container into a cleaning pool of the unloading area in a vertical state; S3, disassembling an outer cover of the transportation container, and arranging a shield plate on an inner cover of the transportation container; S4, opening covers on a drainage hole and an exhaust hole on the inner cover, connecting a radioactive detection device, detecting if the transportation container has radioactive gases or not, if so, stopping unloading, and if not, removing the radioactive detection device, and executing the step S5; S5, filling water into the transportation container and carrying out cooling; S6, disassembling the inner cover of the transportation container; and S7, taking the spent fuel out of the transportation container. The method provided by the invention realizes infield transporting and unloading of the spent fuel in the nuclear power plant, and guarantees empty framework to receive new fuel in the nuclear power plant.