A tolvaptan solid dispersion and its preparation method are disclosed. The solid dispersion comprises tolvaptan and crosslinked polyvinylprrolidone at a weight ratio of 1:0.05-20 preferably 1:0.1-10 more preferably 2:1. The solid dispersion can also comprise water-soluble polymer such as polyvinylprrolidone hydroxypropylcellulose hydroxyethylcellulose or methylcellulose. The weight ratio of tolvaptan : crosslinked polyvinylprrolidone : water-soluble polymers preferably is 2:1:0.1. The solid dispersion exhibits good thermodynamic stability and solubility. The pharmaceutical composition thereof has improved release rate and bioavailability.
