A novel flame retardant(DAPSiO), containing silicon and nitrogen, was synthesized by using dichlorodiphenylsilane,-chloropropyl methyl dimethoxysilane and 1,2-ethanediamine. DAPSiO was used together with potassium-4-(phenylsulfonyl)benzenesulfonate(KSS) to prepare a flame-retardant system for polycarbonate(PC). The structure of DAPSiO was characterized by Fourier transform infrared spectroscopy(FTIR), and1H-NMR tests. Flammability and thermal behaviors of PC/KSS/DAPSiO systems were estimated by limited oxygen index(LOI), vertical burning test(UL-94) and thermogravimetric analysis(TGA) tests. The results showed that the flame retardancy and thermal stability of PC/KSS system were improved with the addition of DAPSiO. When 1 wt% DAPSiO and 0.5 wt% KSS were incorporated,the LOI value of PC was found to be 44, and class V-0 of UL-94 test was passed. The scanning electron microscopy(SEM)and FTIR indicated that PC/KSS/DAPSiO system held a more cohesive and denser char structure when compared with pure PC and PC/KSS system. A novel flame retardant (DAPSiO), containing silicon and nitrogen, was synthesized by using dichlorodiphenylsilane, -chloropropyl methyl dimethoxysilane and 1,2-ethanediamine. DAPSiO was used together with potassium-4- (phenylsulfonyl) benzenesulfonate (KSS) to prepare a flame The structure of DAPSiO was characterized by Fourier transform infrared spectroscopy (FTIR), and 1H-NMR tests. Flammability and thermal behaviors of PC / KSS / DAPSiO systems were estimated by limited oxygen index (LOI), Vertical burning test (UL-94) and thermogravimetric analysis (TGA) tests. The results showed that the flame retardancy and thermal stability of PC / KSS system were improved with the addition of DAPSiO. When 1 wt% DAPSiO and 0.5 wt% KSS were incorporated, the LOI value of PC was found to be 44, and class V-0 of UL-94 test was passed. The scanning electron microscopy (SEM) and FTIR indicated that PC / KSS / DAPSiO system held a more cohesive and denser char structure when compared with pure PC and PC / KSS system.