Lightweight wood-plastic composites (WPC) are made from expandable polystyrene and wood particle using a mold foaming technique, and their fire resistance is improved with the addition of melamine phosphate (MPP) and aluminum hypophosphite (AHP). Flame retardancy is characterized and shown to be significantly enhanced on limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimetry tests. The fire behavior investigation indicates that the LOI value of WPC/12MPP/3AHP sample can reach 33.5% and UL-94 rating was V-0. The total heat release, total smoke production, peak of smoke production rate and peak of heat release rate of WPC/15MPP are reduced by 23.2%, 47.5%, 28.6% and 17.3%, respectively, compare with the pure one. Mechanical properties characterization of composites also reveals that MPP/AHP has a positive influence on the impact strength, modulus of elasticity and modulus of rupture.