The invention discloses an emulsifying agent as well as a preparation method and application thereof. The emulsifying agent is prepared from polyol fatty acid ester, surface active agents with different HLB (Hydrophile Lipophile Balance) values and alkylphenol polyoxyethylene ether; the preparation method comprises the steps of uniformly mixing raw materials, raising the temperature to 60 DEG C, stirring, then cooling to 30 DEG C, filtering and removing impurities. The emulsifying agent is applied to knitting machine oil, has the advantages that the emulsifying agent is colorless, odorless and transparent oily liquid, has no layering and sediment phenomena after long-term storage, and is suitable for emulsifying base oil with the viscosity range being 5 to 30mm<2>/s at 40 DEG C; meanwhile, the preparation process of the emulsifying agent is simple, environment-friendly and free of pollution; in addition, the knitting machine oil obtained by compounding the emulsifying agent with the base oil can be quickly emulsified and dispersed in cold water, emulsion microscopic particle size distribution is uniform, after being stored at room temperature for 24 hours, emulsion has no layering and floating oil phenomena, and the emulsifying agent has an excellent cleaning effect on knitting machine oil draining period equipment or fabric with splashes of oil.