In this study, the insoluble drug, progesterone, was formulated into a progesterone nanocrystal injection to improve the saturation solubility, release rate, and efficacy of progesterone, as well as to increase the relative bioavailability of progesterone, reduce the subsequent irritation, and minimize the toxicity; the advantages and feasibility of the progesterone nanocrystalline injection in the prevention of premature delivery and protection against pregnancy-associated risks in pregnant females was evaluated. The wet grinding method was used to prepare the progesterone nanocrystalline injection; its morphology, particle size, and potential were characterized by transmission electron microscopy. Crystal structure was analyzed by X-ray powder diffraction; the solubility of the injection and the progesterone drug substance in water, and the In Vitro release of the drug were evaluated for its nanometer effect In Vitro. Rabbits were injected with the progesterone nanocrystal injection as well as commercially available progesterone injections for evaluation in vivo. The formulation process of a progesterone nanocrystal injection is feasible. The crystal form is stable and the particle size is uniform. Moreover, we found that it improves the release rate, saturation solubility, and bioavailability of progesterone, while reducing muscle irritation. The results have clinical research significance.