PROBLEM TO BE SOLVED: To provide a composition for thermoplastic polymer films which does not cause deterioration of flow drop performance by friction in film formation or spreading and exerts good flow drop performance through a long period after a film applied with it is spread on an agricultural house, a production method of a modified thermoplastic polymer film using the composition, and a modified thermoplastic polymer film obtained by the production method.SOLUTION: A composition for thermoplastic polymer film coatings comprises a specified modified inorganic cation colloid sol, an anionic surfactant and a specified (poly)glycerol in a specified ratio.SELECTED DRAWING: None