The interaction of phosphorus flame retardant and layered clays and silicates on the flame retardant effect of polyurethane was focused by researchers. Lorenzetti et al. [14] reported that when layered silicate was combined with phosphinates, the thermo-oxidative stability of RPUF was better, but its flame retardancy was no better than that of RPUF with mere phosphinates. We [15] had reported that the interaction of phosphorus flame retardants and nano calcium carbonate in RPUF could form ceramic substance in the char, it could protect the char from thermo-oxidative degradation. Modesti et al. [16] studied RPUFs with aluminum phosphinate and different type of MMTs, that were pristine montmorillonite, ammonium modified clay and diphosphonium modified clay. The results showed that the addition of MMT, especially diphosphonium modified clay, was helpful in the increase of limit oxygen index (LOI) of RPUFs. Besides, the results in our previous research [17] showed that MMT was less effective on decrease of HRR of RPUF with APP/TPP as a composite flame retardant, but could decrease SPR of RPUF.