The invention discloses a preparation method of a tolvaptan tablet. The preparation method comprises the following steps: 1, mixing tolvaptan with high-substituted hydroxylpropyl cellulose according to a mass ratio of 1:0.2-0.6, crushing them, and sieving by a 60-100 mesh sieve; 2, dissolving throughs in a mixed solution of waterless ethanol and dichloromethane with a volume ratio of 1:1-4, carrying out spray drying to form powder, carrying out reduced pressure drying at 70-90DEG C until that the content of solvents residual in the sprayed powder is qualified; 3, crushing the sprayed powder, sieving by a 180-220 mesh sieve, accurately weighing the sprayed powder, lactose, microcrystalline cellulose and hydroxypropyl methylcellulose according to prescription amounts, uniformly mixing them, and adding a proper amount of water to prepare a soft material; and 4, sieving the soft material by a 15-25 mesh sieve, preparing a wet particle, drying the wet particle at 50-70DEG C until that the content of water in the wet particle is 2-4%, sieving the dried wet particle by a 15-25 mesh sieve, granulating, adding a prescription amount of magnesium stearate, uniformly mixing, and tabletting. The preparation method of the invention has the advantages of ingenious conception, low production cost, high in vitro dissolubility of the prepared tolvaptan tablet, and good biological availability and clinic curative effect of the tolvaptan tablet.