The present invention provides a crystalline form of dextral oxiracetam. The crystalline form has a diffraction peak when a diffraction angle, 2θ, is 17.76±0.2°, 20.16±0.2°, 21.20±0.2°, 24.17±0.2°, or 25.88±0.2°. The crystalline form of dextral oxiracetam can promote synthesis of phosphorylcholine and phosphoethanolamine, boosts cerebral metabolism, has a stimulating function on a specific central nervous pathway through a blood-brain barrier, and has special biological activity in the field of sedation and the antiepileptic field. The crystalline form of dextral oxiracetam of the present invention is a water-containing crystalline form, contains 0.5 water molecules, loses crystallization water at 73.5±2° C., and is melted and decomposed at 138.0±2° C. The crystalline form of dextral oxiracetam of the present invention can stably exist at room temperature and relative humidity of 0-95%, does not transform, is used for storage and formulation processing, and has low requirements for processing or storage humidity.