Abstract: The flame-retardant polyurethane (TPU) composites were prepared by using triazine charring-foaming agent and ammonium polyphosphate as intumescent flame retardants (IFR) and silica and magnesium silicate as synergistic agents. The flame retardant performance, mechanical properties, thermal decomposition behavior, surface morphologies and elemental compositions of char layers were investigated comparatively. The results indicated that the specimens with a thickness of 1.6 mm achieved a UL 94 V-2 classification when the total loading amount IFR of 30 wt % was added along with 5 wt % SiO2 corresponding to the IFR. However, a UL 94 V-0 classification was gained when 26 wt % of IFR and 5 wt % of MgSiO3 were incorporated. These results indicated that MgSiO3 could generate a good antidripping effect on the flame retardant system. Moreover, the incorporation of MgSiO3 had less influence on the tensile properties compared to SiO2. XPS analysis indicated that the introduction of MgSiO3 into the IFR/TPU composites improved the phosphorous content in the formed char layer. SEM observation demonstrated that MgSiO3 promoted the formation of a more continuous and compact char layer with higher strength during combustion. Consequently, the flame retardant performance of the composites was enhanced.