The invention discloses a preparation method of a special emulsifier for a rosin emulsion and belongs to the technical field of deep processing of rosin. The preparation method adopts raw materials in parts by weight as follows: 5-8 parts of cardanol, 1-2 parts of polyethylether modified trisiloxane, 6-10 parts of ethanol, 0.1-0.2 parts of lignin sulfonate, 15-25 parts of lauryl sodium sulfate and 10-15 parts of deionized water with electric conductivity smaller than 5 mu S/cm; the preparation method comprises steps as follows: the deionized water is added to a reactor firstly, the pH value of the deionized water is regulated to 9, cardanol, polyethylether modified trisiloxane, ethanol, lignin sulfonate and lauryl sodium sulfate are added, a mixture is heated to 80-95 DEG C and subjected to a reaction for 0.5 h, and then the mixture is cooled to 55-65 DEG C for 1 h and is heated to 80-95 DEG C and subjected to a reaction for 0.5 h. The preparation method is used for preparation of the rosin emulsion, and has the advantages of high emulsification activity and high stability.