The toughness and flame retardancy of glass fiber (GF)-reinforced polycarbonate (PC) composites were tested by adding four impact modifiers and three kinds of flame reardants. Silicon acrylate rubber (SiR) could significantly toughen the composites by 2.52 times. Then only by addition of 0.2 wt% oligomeric siloxane-containing potassium dodecyl diphenylsulfone sulfonate (SiKSS), PC/GF/SiR composites can achieve good flame retardancy with a V0 rating in UL-94 burning vertical test. This formulation also maintained the system a relative high heat deflection temperature around 120 °C.