Abstract A novel of flame retardant (FR), oligomeric siloxane containing triphenylphosphonium phosphate (SiPP), has been synthesized from triphenylphosphine and 3-chloropropylmethyldimethoxysilane as starting materials. After blend with polycarbonate (PC), the Limiting Oxygen Index (LOI) values increased with the increase of SiPP contents and reached 30.9 when the SiPP content was 20 phr, and the V-0 rating can be achieved when only 5 phr SiPP was blended. The morphological structures of the char formed after PC/SiPP burnt in LOI test were investigated by Scanning Electron Microscopy (SEM). The heat release rate (HRR) and total heat release (THR) were dramatically reduced with the increase of the SiPP content of the PC composite. The thermal stability, mechanical properties and morphological feature of PC/SiPP composite were also investigated.