The invention discloses 2-(Alpha-hydroxyl amyl) 
potassium benzoate polymorphism as well as a preparation method, a preparation and an application thereof. A characteristic 
diffraction peak is displayed by an X-
ray diffraction pattern of the polycrystalline 
powder at a reflection angle within 2Theta+ / -0.1 DEG of 7.0, 20.8 and 26.4+ / -0.2 DEG. The preparation method comprises the following step: carrying out 
crystallization by selecting one or any combination of methyl 
alcohol, absolute ethyl 
alcohol, 95% ethyl 
alcohol, 75% ethyl alcohol, 50% ethyl alcohol and 2-
butanol and selecting one or any combination of normal propyl alcohol and 
isopropyl alcohol or selecting the normal 
butanol. The preparation is of tablets, capsules, granules, a freeze-dried 
powder injection and an injection liquid, which is prepared by adding pharmaceutically acceptable carriers and auxiliary materials into the 2-(Alpha-hydroxyl amyl) 
potassium benzoate polymorphism. The 2-(Alpha-hydroxyl amyl) 
potassium benzoate polymorphism is applied to a 
medicine for treating a neurodegenerative 
disease. The 2-(Alpha-hydroxyl amyl) 
potassium benzoate polymorphism is stable in performance and suitable for industrial production, thereby laying the foundation for the development of a 2-(Alpha-hydroxyl amyl) 
potassium benzoate medicine.