A tolvaptan solid dispersion and its preparation method are disclosed. The solid dispersion comprises tolvaptan and cross-linked polyvinylprrolidone at a weight ratio of 1:0.05-20, preferably 1:0.1-10, and more preferably 2:1. The solid dispersion can further comprise one or more water-soluble polymers, such as polyvinylprrolidone, hydroxypropyl cellulose, hydroxyethyl cellulose or methylcellulose, wherein the weight ratio of tolvaptan:the crosslinked polyvinylprrolidone:the water-soluble polymers is preferably 2:1:0.1. The solid dispersion exhibits good thermodynamic stability and solubility. The pharmaceutical composition thereof has improved release rate and bioavailability.
