OBJECTIVE：To prepare Brevisc apine（BRE） nanocrystals，and to evaluate its quality. METHODS ：BRE nanocrystal suspensions were prepared by media milling method. The diameter and amount of grinding beads ，grinding time ，type and ratio of stabilizer ，BRE ratio were investigated to screen the optimal technology and formulation with particle size and polydispersity index （PDI） as evaluation indexes. Using morphology ，color，particle size and PDI of BRE nanocrystals as evaluation index ，different lyoprotectants （50％ mannitol，5％ glucose，5％ lactose）and without lyoprotectant were investigated to screen the optimal lyoprotectant. Particle size analyzer ，scanning electron microscope （SEM），X-Ray diffraction （XRPD）， differential scanning calorimeter （DSC）were used to evaluate the quality of BRE nanocrystals which was prepared with the optimal technology and formulation. RESULTS ：The optimal technology and formulation of BRE nanocrystals included that particle size of 0.6 mm zirconia beads with the amount of 450 g，grinding time of 1 h，stabilizer of 15％ Tween-80，BRE ratio of 25％，without lyoprotectant. Prepared BRE nanocrystals were yellow powder with loose texture and uniform color. The average particle size of BRE nanocrystals was （283.10±3.08）nm，average PDI was （0.212±0.021）and average Zeta potential was （－38.48±0.39）mV. BRE nanocrystals were rod-like crystals ，uniform in distribution and had no change in crystalline state. Accumulative dissolution of BRE nanocrystals were （90.37±1.22）％ within 20 min. Under the condition of （40±2）℃ temperature and （75±5）％ relative humidity，BRE nanocrystals remained stable after being kept away from light for 3 months. CONCLUSIONS ：Established preparation method of BRE nanocrystals is simple and feasible. Prepared BRE nanocrystals show good stablility and dissolution.