Within this work, a novel eco-friendly flame-retardant system for wood plastic composites (WPCs) was developed based on the phytic acid modified wood flour (WF) and the silane-coupling agents treated diatomite, were incorporated into low density polyethylene (LDPE) by a melt-blending process. Via impregnation process, neutralized phytic acid (PA(N)) was absorbed into the wood porous structure to obtain phytic acid modified wood flour (WF-PA(N)), which was expected to improve the retardancy and thermal stability of the WPC composites without deterioration of their mechanical properties. Moreover, polyethylene grafted maleic anhydride (MAPE) could render the phytic acid modified woods to be well dispersion in LDPE matrix, and consequently increasing the thermal resistance properties of the composites with increasing the content of the phytic acid modified woods. The TGA analysis revealed that the char yield of the LDPE/WF-PA(N) composites (22~29%) were higher than that of LDPE/WF (14%), indicating improved thermal stability by the addition of WF-PA(N). The heat distortion temperature (HDT) of the LDPE/WF-PA(N) composites exhibited upward with increasing WF-PA(N) contents. Among the LDPE/WF-PA(N) composites, the one containing 45% of WF-PA(N) exhibits the best tensile and impact strength. In addition, the burning rate analysis demonstrated that LDPE composites containing WF-PA(N) has short burning rates presumably ascribed to the formation of char layer from phosphoruscontaining additives WF-PA(N). This is consistent with the results of TGA analysis.