Abstract: The present invention relates to a pre-processing method for the purpose of formulating a drug substance having non-uniform particle sizes by a manufacturing method having excellent manufacture performance. According to the pre-processing method of the present invention, additives including at least a dispersant are blended in a drug substance having a specific particle size distribution and then the resultant mixture is deagglomerated/sized to disperse and make adhere the additives onto the surfaces of the particles of the drug substance, thereby yielding a powder having a specified particle size distribution. In this manner, a pharmaceutical preparation can be manufactured with excellent manufacture performance, manufacture efficiency, and manufacture cost by a direct compression method, a wet continuous granulation system or the like. Therefore, the pre-processing method is very useful.