Abstract: Nanocrystal technology changes the solubility and dissolution rate of insoluble drugs by reducing the particle size to the nanometer level. This technology is not limited by carrier materials and encapsulation rate. It is suitable for a variety of drug delivery routes and easy for industrial production. It has gradually become a cutting-edge hot technology in the international pharmaceutical field to improve the absorption of insoluble drugs and improve their bioavailability. This article introduces the influencing factors and challenges of nanocrystal drugs (NC) in parenteral, ocular, transdermal and pulmonary administration, and focuses on nanocrystal drugs that have been marketed or are still in the preclinical or clinical trial stages of these delivery systems, in order to provide some insight for the further development of poorly soluble drug nanocrystal preparations.