The invention discloses a preparation method of Azelnidipine of alpha crystal form, wherein, Azelnidipine of non-alpha crystal forms is completely dissolved in a two-phase organic solvent. Water-bath is heated to certain temperature and alkane and seed crystal are added into the solution under a stirring condition. A crystal is separated out by cooling and a separated crystal product is collected, namely the Azelnidipine of alpha crystal form. The two-phase organic solvent comprises two components: low boiling point esters and benzene or derivatives of benzene, with a volume ratio of 1 to 3:15. The preparation method has one-time yield up to 85 percent to 90 percent, purity of more than 99.5 percent as well as good appearance and quality. The preparation method has easily recycled organic solvent, is beneficial to environmental protection, reduces loss in Azelnidipine and/or waste in the organic solvent, greatly reduces the production costs of products and has prospect of large-scale industrialized production.