The invention relates to a preparation method of a water shield buccal tablet. The method comprises the following steps of: A. picking water shield tender tips and young leaves, which are all green in the leaf bodies and contain transparent colloid on the backs of the leaves, washing the tips and leaves, carrying out microwave deactivation of enzymes for 8-10 minutes, separating the water shield colloid and then carrying out vacuum freeze drying; B. soaking the dried colloid in anhydrous alcohol in a ratio of 1-5:1 by weight, and wet-milling and crushing the colloid at a rotation speed of 30-60r/min for 15-20 minutes, to obtain water shield colloid mash; C. uniformly mixing and wetting 10-80% of water shield colloid mash, 10-35% of maltodextrin, 5-45% of sugar and 5-10% of microcrystalline cellulose in percentage by weight; D. sieving the wetted mixture by using a standard sieve with 20, 30 or 40 meshes, drying the sieved mixture at 40-50 DEG C, and then sieving the mixture by using the standard sieve with 20, 30 or 40 meshes to obtain the dried mixture; and E. mixing the dried mixture with magnesium stearate which is 1.5-2% of the total amount of the dried mixture, and carrying out tabletting to obtain the water shield buccal tablet.