Red phosphorus encapsulated by polysiloxane (MRP) was prepared, and the chemical structure and morphology of MRP were characterized by FTIR and TEM, respectively. A series of flame retardant polycarbonate/acrylonitrile-butadiene-styrene containing MRP (PC/ABS/MRP) were prepared via melt-blending. The flame retardance of PC/ABS/MRP was investigated by limiting oxygen index (LOI) and UL-94 test. It was shown that the LOI value was increased to 27.7 and UL-94 achieved a V-0 rating at a 15 wt % loading of MRP. Cone calorimetric results showed that the peak of heat release rate (PHRR) of PC/ABS/15% MRP decreased from 452.7 to 198.0 kW/m(2), and the total heat release decreased from 92.9 to 60.7 MJ/m(2) compared with virgin PC/ABS. Thermal stability analysis showed that the char yield of the PC/ABS/15% MRP increased from 0 to 16.1 wt % under air atmosphere, and from 15.2 to 27.4 wt % under nitrogen atmosphere compared to virgin PC/ABS, respectively. The sample PC/ABS/15% MRP also showed excellent water resistance of flame retardance in 70 degrees C water for 168 h. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2867-2874, 2012