The invention relates to a fiber fully drawn yarn (FDY) spinning oil which comprises a high-temperature smoothing agent, a composite antistatic agent, a bundling agent, a phenolic group antioxidant, a phenylamino group antioxidant, an olefine acid antioxidant, a high-temperature dispersant, a softening agent, an environment-friendly emulsifying agent, a defoaming agent, a preservative and an environment-friendly penetrating agent, wherein the high-temperature smoothing agent comprises hydrogenation paraffin-based oil and hydrogenation naphthenic oil. The invention also provides a preparation method of the fiber FDY spinning oil. The fiber FDY spinning oil is stable in emulsion and free from stratification and odor, and is not easily rotted; the fiber is easily not yellowed by dyeing, and the fiber FDY spinning oil is easy to rinse; the production process is stable, and the fiber FDY spinning oil has few broken ends, is good in heat resistance, does not have smoke formation, is not coked on a hot roller, has the excellent anti-static performance under the different humidity conditions, and thus the fiber FDY spinning oil can meet the requirements of high-speed spinning technologies of various specifications of fiber including thick fibers and thin fibers; after the fiber FDY spinning oil is used, the fiber can smoothly pass through the after the spinning of various equipment, so that the yield and the good rate of fiber spinning can be effectively increased.