The invention discloses a quaternary ammonium hydroxypropyl sodium phosphate quick breaking asphalt emulsifier and a preparation method thereof. The asphalt emulsifier is prepared from the following raw materials according to molar ratio: octadeyl dimethyl tertiary amine, an alcohol solvent, epoxy chloropropane and sodium dihydrogen phosphate with the molar ratio of 1mol to (4.00-9.00)mol to (1.00-1.15)mol to (1.50-1.73)mol, or octadeyl dimethyl tertiary amine, an alcohol solvent, epoxy chloropropane, rtiary sodium phosphate and hydrochloric acid with the molar ratio of 1mol to 4.00-9.00)mol to (1.00-1.15)mol to (1.30-1.50)mol to (1.40-1.61)mol. The alcohol solvent adopts ethanol, methanol or isopropanol. The asphalt emulsifier has the advantages that the raw materials are available, the production cost is low, the technology is simple, and high-temperature reaction is not required, various different models of asphalt can be emulsified, formed emulsified asphalt is fine and uniform, the storage stability is good, and cationic emulsified asphalt can be prepared.