The invention belongs to the technical field of nuclear assistant cooling water of 1000MW nuclear power plants, and particularly relates to a positioning method of a grid frame in a spent fuel pool ofa 1000MW nuclear power plant. The method is used for positioning the grid frame. The method comprises the following steps: S01, supplying a first grid frame positioning structure which is capable ofadjusting the expanding length; and fixing the first grid frame positioning structure to the first side of a new grid frame; S02, adjusting the expanding length of the first grid frame positioning structure to be a preset space between the previous grid frame and the new grid frame; S03, supplying a hoisting device; lowering the new grid frame into the spent fuel pool of the 1000MW nuclear power plant through the hoisting device; and moving the new grid frame until the first grid frame positioning structure is propped between the new grid frame and the previous grid frame; and S04, supplying apushing device for pushing the new grid frame to be levelled to the previous grid frame. Therefore, a sufficient space is supplied after the new grid frame and the previous gird frame are mounted, and the new grid frame and the previous grid frame cannot influence each other, moreover, the space between the new grid frame and the previous grid frame is reduced, and as a result, the space waste ofthe spent fuel pool of the 1000MW nuclear power plant is avoided.