Aiming at the application of the cold-chain logistics in freezing temperature area, a composite phase change material for cold storage which is composed of trimethylolpropane , ammonium chloride and H₂O was proposed. The composite phase change material with excellent thermal performance was developed by using differential scanning calorimetry, which has a mass ratio of 1∶2∶7 with phase-change temperature of -19.4 ℃ and latent heat enthalpy of 250.5 kJ/kg. Then, the effects of cooling rate, temperature of cooling medium, vessel diameter and different nanoparticles （Al₂O₃，Fe₂O₃，TiO₂）on the supercooling degree were experimentally investigated. The results show that when the cooling rate decreases from 1.89 ℃/min to 0.47 ℃/min, the reduction range of supercooling degree is 40.9%. When the temperature of cooling medium increases from -30 ℃ to -24 ℃, the maximum reduction range of supercooling degree is 48.5%. When the vessel diameter increases from 10 mm to 20 mm, the reduction range of supercooling degree is 39.5%. When the concentration of TiO₂ is 0.4%, the optimum effect on reducing supercooling degree is achieved. Therefore, the supercooling degree can be effectively reduced by reducing the cooling rate, increasing the temperature of the cooling medium and the size of the vessel, and adding a certain amount of TiO₂ nanoparticles.