The invention discloses a determination method for a light scattering / fluorescence ratio of PFOS (Perfluorooctane Sulfonates) in an environment water sample, and in particular relates to the field of environment analysis. The determination method comprises the following steps of: orderly adding 0.2 mL of rhodamine solution B with the concentration of 5.0x10<-4> mol / L and 0.5 mL of BR buffer solution with pH of 1.81 into 10 mL of colorimetric cylinder by adopting a light scattering / fluorescence ratio analysis method, swirling uniformly, and adding a pre-treated water sample to be treated; after swirling uniformly, carrying out constant-volume operation to 5 ml by ultra-pure water of 18.2 MW; after swirling uniformly, instantly exciting on a fluorospectro photometer at a 332 nm place, and scanning an emission spectrum of 220-650 nm to obtain a resonant light scattering / fluorescence emission spectrum, wherein an excitation slit and an emission slit are 2.5 nm and the voltage is 700 V; and carrying out initial quantitative analysis and quantitative analysis to check whether the environment water sample contains PFOS according to a ratio I340 / F596 of a light scattering intensity (I340) at a 340 nm place to a fluorescence intensity (F596) at a 596 nm place. If a light scattering signal at the 340 nm place is enhanced and a fluorescence signal at the 596 nm place is reduced, the water sample contains the PFOS; otherwise, the water sample does not contain the PFOS or the content of the PFOS is lower than a detection limit. The determination method, provided by the invention, is used for PFOS detection in the environment water sample, and has characteristics of simpleness, speediness, sensitiveness and low detection cost.