To provide a method for preparing a cellulose acylate solution in good solubility by a cooling dissolution method and a high pressure dissolution method using a non-chlorinated organic solvent substantially not using a chlorinated hydrocarbon such as methylene chloride, to provide a cellulose acylate film having excellent planarity and free from fubbles from the solution, and to provide a method for producing the same.

This method for preparing a cellulose acylate solution comprises preliminarily cooling a used organic solvent 1 at -100 to -10°C with a cooler 2, introducing the cooled organic solvent from a port 9 for introducing the organic solvent into a mixing pot 3 with a heat-insulating jacket 5, stirring the introduced organic solvent with a stirrer 4, transporting a cellulose acylate 6 stored in a silo 7 with a cutting and transporting machine 8, introducing the cellulose acylate from a cellulose acylate introduction port 10 into the mixing pot 3, and simultaneously mixing the introduced cellulose acylate with the cooled organic solvent. Thus, the cellulose acylate is immediately swollen. This method comprising introducing the cellulose acylate into the low temperature organic solvent makes it possible to more largely shorten the swelling time than by a conventional method comprising mixing the cellulose acylate with the organic solvent and subsequently cooling the mixture. The swollen mixture is transferred from a mixture-discharging port 11 to the next process.