The invention discloses a method for determining total organic fluorine in water based on ultraviolet sulfite pretreatment, and the method comprises the following steps: performing non-selective degrading defluorination on various perfluoro/polyfluoric organic compounds (PFCs) including the organic compounds most difficult to degrade such as perfluorooctane sulfonate (PFOS) in contaminated water bodies (including drinking water, surface water and industrial wastewater, etc.) to convert organic fluorine in aqueous solution to inorganic fluoride ions, and determining the concentration of fluoride ions to obtain the amount of total organic fluorine in the water sample. The reagents and instruments used in the method are highly available, and the cost of the determination is greatly reduced compared with the current mainstream methods, and the whole process is easy to implement.