A composite phase change material and the method for forming the material is disclosed herein. Thereof, especially a composite phase change material for lithium battery cooling, comprising polyethylene glycol, silica vehicle and composite flame retardant comprising graphite and polymer, wherein the weight ratio of the graphite and polymer is approximately 1:2. The composite phase change material according to the invention has a good stability and a thermal conductivity, a small corrosivity, a high phase transition enthalpy of 150-350 J/g, and a morphological stability during phase change. Moreover, addition of high thermal conductivity material and composite flame retardant ensures good thermal conductivity and excellent flame retardant effect of the phase change material.