A flame retardant (DPA-SiN) containing phosphorus, nitrogen and silicon elements was synthesized. The halogen free flame retardant was incorporated into PC/ABS to improve its flame retardancy. The flame-retardant properties of the PC/ABS/DPA-SiN blends were estimated bylimiting oxygen index (LOI) values and CONE Calorimeter, while thermal stabilities were investi-gated through thermo gravimetric analysis (TGA). The PC/ABS/DPA-SiN blends were thermally de-graded at 400 ℃ for different amounts of time and studied by Fourier transform infrared spectros-copy (FTIR) to better understand the degradation behavior of PC/ABS/DPA-SiN.