The invention relates to paper flocking adhesive and a preparation method thereof. By referring to Figure 1 in the abstract, the process steps and components are as follows: dissolving an emulsifier into deionized water to obtain an emulsifier water solution, adding a mixed monomer in which rosin is dissolved into the emulsifier solution, and shearing and dispersing by using a dispersing homogenizer (600-700r/min, 15min) to prepare a monomer pre-emulsion; adding the deionized water into a four-mouthed flask with a refluxing device, heating to 80 DEG C, dropwise adding a monomer pre-emulsion and an initiator water solution while stirring (150-300r/min), completing drop-by-drop addition after 1.5h, preserving heat and reacting for 0.5h at 85 DEG C, naturally cooling, adjusting pH, and filtering to obtain the paper flocking adhesive. According to the preparation method, as the rosin is taken as a tackifier, and the advantage of a molecular weight regulating effect of the rosin is utilized, the adhesive, which is low in viscosity, good in infiltration and strong in adhesion and is suitable for flocking hard paper such as a pulp mould, a paperboard and a corrugated paperboard and the like, is prepared.