The invention discloses a preparation method of a novel bromelain preparation. The preparation method comprises the following steps: (1) preparing pineapple juice; (2) preparing a natural polyanion polysaccharide solution; (3) respectively adjusting the pineapple juice and the natural polyanion polysaccharide solution until the pH values are the same, adequately mixing the pineapple juice with the natural polyanion polysaccharide solution, and stirring to generate a bromelain-polyanion polysaccharide compound precipitate through an electrostatic attraction interaction between the bromelain and polyanion polysaccharide in the pineapple juice; and (4) centrifugally collecting the bromelain-polyanion polysaccharide compound precipitateand drying, so as to obtain the bromelain preparation. By utilizing a principle of generating the precipitate by virtue of the electrostatic attraction interaction between the bromelain and polyanion polysaccharide, the bromelain is separated, and the bromelain preparation is obtained. The bromelain preparation has the stability of bromelain in storage and processing processes and has good slow-release and control-release properties, and the disadvantages that bromelain is sensitive to head and easy to oxidize can be overcome.