[Problem] To provide a composition for film formation comprising cellulose fibers, a layered inorganic compound, and a water-soluble polymer, which are each dispersed on nano level, a method for preparing a cellulose dispersion capable of forming a moisture-resistant film containing cellulose nanofibers, a gas-barrier laminate obtained by use of the dispersion, and a packaging material using the laminate. [Solution] A film-forming composition comprising at least cellulose fibers and a swollen inorganic compound is prepared. The method of preparing a cellulose dispersion comprises the steps of oxidizing cellulose, fibrillating the thus oxidized cellulose to prepare cellulose nanofibers, and adding a water-soluble polymer and inorganic particles to the dispersion containing the cellulose nanofibers.