This report presents a simple, sensitive and selective victoria blue B (VBB)-based resonance light scattering (RLS) assay of perfluorooctane sulfonate (PFOS). In pH 6.0 KH2PO4-NaOH buffer solution, VBB can be protonated and reacts with PFOS through electrostatic interactions to produce ionic-association complexes. Simultaneously, the interaction leads to enhanced resonance light scattering intensities greatly, which are characterized with a peak at 277 nm. It is found that the enhanced RLS intensity is proportional to the concentration of PFOS in a range of 0.05 to 4.0 μmol·L-1. The limit of detection is 5.0 nmol·L-1. While, under the optimal experimental conditions, almost no change of the resonance light scattering intensity was observed between VBB and perfluorooctane acid (PFOA) which is one kind of representative perfluorinated compounds (PFCs). The excellent selectivity of PFOS could be due to the hydrophobicity of PFOS higher than PFOA. It is worth noting that the proposed method is capable of differentiating PFOS and some other PFCs. UV/Vis absorption spectrum and scanning electron microscope (SEM) image both were investigated to further validate the reaction mechanism. The interference of coexisting foreign substances and the optimum tests of reaction conditions, including pH value, reaction time, experimental temperature and ionic strength, were also investigated. This method has been successfully applied to the determination of PFOS in environmental water samples with RSD ≤1.74%. The experimental process as followed: In 2 mL colorimetric tube, 200 μL pH 6.0 KH2PO4-NaOH buffer solution, followed by adding 600 μL 20 μmol·L-1 VBB solution, swirl evenly, then add the right amount of PFOS solution. After vortex mixing with ultrapure water volume to 2 mL, swirl to mix, stand for 10 min at room temperature. Then the mixture was transferred for RLS measurements and absorption measurement.