The invention discloses a paraffin emulsion and a preparation method thereof; based on the total amount of the paraffin emulsion, the paraffin emulsion consists of 30-60 mass% of solid paraffin, 2-8 mass% of a composite emulsifier and 32-68 mass% of water. The solid paraffin and the compound emulsifier only need to be added in a reaction kettle with stirring paddles, and after uniform stirring, water is slowly added drop by drop at a certain temperature, and thus the paraffin emulsion can be prepared. In the preparation of the paraffin emulsion, the compound emulsifier does not need to be heated and melted or dissolved in a solvent, water for emulsification does not need to be heated during emulsification, the prepared emulsified paraffin does not contain organic solvents, the viscosity ofthe emulsion is low, a formed film is uniform, the particle size is small, the dispersity is good, the storage stability is good, and the emulsified paraffin is prone to combined use with aqueous solutions or emulsions of other substances; the paraffin emulsion has the advantages of being safe, efficient, economical and convenient, and can meet the requirements of low paraffin consumption amountand good water resistance of waterproof agents in fiberboard industry.