After adding coagulant in diesel fuel, when the temperature is lowered and the wax crystal is formed, the coagulant will play the role of nucleating agent and wax crystal together or adsorbed on the surface of the wax crystal, preventing the mutual bonding between the wax crystal, preventing the generation of a continuous crystalline network, making the wax crystal particles more fine and can pass through the filter well. This destruction or change of wax crystallization function of the coagulant can reduce the cold filtration point and freezing point of diesel fuel.