Latent heat storage using organic phase change materials (PCMs) have the potential to alleviate the contradiction between supply and demand in energy. However, the usage of PCMs is compromised by deficiencies including liquid leakage during liquidation and solidification, poor thermal conductivity and inferior thermal stability. Herein, we successfully fabricated a series of novel form-stable phase change materials (FSPCMs), using the polyolefin elastomer (POE) along with the octadecylamine-functionalized graphene (C18-rGO) acted as the supporting networks and paraffin as the thermal energy storage material. The octadecyl chain incorporated on the surface of graphene not only prevented from the graphene aggregation, but also endowed excellent structural stability to the composite FSPCMs. Meanwhile, the toughness of the composites was further improved with the addition of POE. Paraffin was tightly imprisoned in the frameworks formed by POE and the C18-rGO, resulting in no leakage even above their phase change temperature. As expected, the composite FSPCMs demonstrated reliable thermal stability and high thermal energy storage capacity. In particular, the composite FSPCMs was capable of absorbing or releasing stored thermal energy at a high rate, illustrating a great potential to be used as the effective thermal energy storage and thermal management systems.