The new hybrid flocculant polyaluminum chloride-poly (dimethyl diallyl ammonium chloride) (PAC-PDMDAAC) was used to treat disperse violet and reactive brilliant red dye wastewater. The experimental results indicated that the decolorization effect of hybrid PAC-PDMDAAC was better than that of PAC and composite PAC-PDMDAAC. The decolorization rates of disperse violet and reactive brilliant red dye wastewater were 99% and 86.8% respectively when the dosages of hybrid flocculant were 400 and 450　mg·L-1. When the pH of disperse violet wastewater was 7～12, the hybrid flocculant had the best decolorization effect. When the pH of reactive brilliant red wastewater was 7～9, the hybrid flocculant had the best decolorization effect. Each of the two dyes and their flocs were characterized with FTIR. Results showed that the hybrid flocculant had a complex reaction with the dye wastewater, and the main decolorization mechanism was charge neutralization and adsorption bridging capacity. The UV scanning results indicated an adsorption peaks shift and an absorbance decreases, which further explained the main mechanism above. At the same time, it also indicated the ether linkage and —NH2 of disperse violet were destroyed and replaced by hybrid flocculant, and the -SO3 , Cl－ of reactive brilliant red were also replaced. The study will provide a new method in decolorization effiency and decolorization mechanism for the new inorganic-organic hybrid polymer flocculant. And it has significant practical meaning and application value.