Petroleum resin is a solid or liquid polymer polymerized under one component(alkene) and two component(alkene) in the byproducts-C5, C9 distillates which are obtained in the course of cracking hydrocarbon into ethylene. According to the different material used, petroleum resins may be divided into aliphatic petroleum resin (C5 distillate polymer), aromatic petroleum resin(C9 distillate polymer), aliphatic and aromatic copolymer resin (copolymer of C5, C9 distillates) and alicyclic petroleum resin (aromatic petroleum hydrotreating resin). C5 hydrotreating resin is normally used in producing hot-melting gel, pressure-sensitive gel, roadside-sign paint, paper sizing agent, etc, for it possesses the performance of decreasing condensation and increasing adhesion, and improving viscosity co-efficient. And the hydrotreating C5 resin has the features of colorlessness, tastelessness, good endurance to heat and weather, so it can be specially used in producing cohesive hot-melting gel for package of sanitary appliances, foods and medicine.