Abstract: The preparation of halogen-free and fluorine-free thin-wall flame-retardant polycarbonate (PC) with low smoke and heat release was a challenge in the field. Polyborosiloxane (PBS) flame retardant was prepared by polycondensation reaction between octamethyl cyclotetrasiloxane and boric acid, and then compounded with boron-phenolic resin (LPR) to prepare PBS-LPR/PC composites. The results show that when the total amount of PBS and LPR is 10wt% and the mass ratio is 3∶1, the best flame-retardant effect is shown in PC, the 1.6 mm thick PC sample can pass UL-94 V-0 rating. Compared with that of pure PC, the peak heat release rate (pHRR), the peak smoke production rate (pSPR), the total heat release (THR) and the total smoke production (TSP) of sample reduces by 76%, 64%, 49% and 65%, respectively. The investigation on flame-retardant mechanism show that LPR decreases the viscosity of PC composites first and then increases, which confirms the generation of cross-linking reaction. The notched impact strength of 7.5%PBS-2.5%LPR/PC is 2.3 times that of PC, which makes the material show high toughness.