In the particulate design for dry powder inhalation (DPI), the drug particles are required to have a good flowability in handling and dispersibility in delivering the drug to lung in order to treat effectively the pulmonary and systemic diseases. In this study, the preparation process of drug particles for DPI using a novel supercritical carbon dioxide freeze granulation based on the rapid expansion of supercritical solutions (RESS process) has been developed. When a drug dissolved into supercritical carbon dioxide is sprayed from a nozzle, frozen carbon dioxide lumps generate owing to the rapid temperature drop (i.e., Joule-Thomson effect), resulting in the granulation of fine drug particles. The granules obtained under the conditions of lower temperatures and higher pressures of supercritical carbon dioxide, in which more frozen carbon dioxide lumps generate, have a good flowability and dispersibility because of increasing in the granule size and decreasing in the bulk density.