In this paper, the adsorption characteristics of cationic polyelectrolyte PDADMAC on BGF particles and the Zeta potential of BGF particles have been investigated. A new type of composite abrasives slurry was obtained with cationic polyelectrolyte modified BGF particles and its polishing performance was studied. Experimental results showed that the Zeta potential of the modified BGF particles was changed from negative to positive and the maximum value (+35mv) was obtained when the adsorption saturation was achieved, and the adsorption capacity of SiO2 abrasives on BGF particles was improved significantly. The material removal rate was 469nm/min with the modified BGF/SiO2 composite abrasives slurry containing 5% SiO2 and 3% modified BGF particles, increasing by 47% and 89% than those of the unmodified BGF/SiO2 composite abrasives slurry (319nm/min) and the single silica abrasives slurry (248nm/min), respectively.