The relationship between adsorption behavior and photocatalytic mechanism of the two dyes wasinvestigated. Adsorption isotherms showed that the adsorption of cationic pink FG was Langmuir type behavior,while the reactive brilliant red k-2G was Freundlich type behavior. The increasing pH favored the adsorption of FGbut have little effect on the photodegradation. The increasing pH favored the adsorption and the photodegradation ofradicals scavenger tetranitromethane inhibited the photodegradation of FG. These results indicated that thephotodegradation of FG mainly via free radicals in solution, and the photodegradation of k-2G was mainly on theeffect of SO2-4 , HCO-3 on the adsorption and photodegradation of two dyes confirmed these results.