The invention discloses a process for preparing irbesartan ultrafine particles by applying a supercritical anti-solvent technology, and belongs to the technical field of medicinal dosage forms and supercritical technologies. The method is characterized in that an irbesartan solution is sprayed into a crystallization kettle through a supercritical fluid anti-solvent equipment system, and brick-shaped and amorphous-state irbesartan ultrafine particles are crystalized and precipitated in the crystallization kettle. According to the process, the shape and particle size of a medicament are controlled by changing parameters such as a solvent type, solution concentration, a solution sample introduction rate, a crystallization pressure and crystallization temperature. The irbesartan ultrafine particles prepared by the process have the advantages small particle sizes and narrow grain size distribution, and the dissolution rate and equilibrium solubility of the medicinal fine particles are improved remarkably.