The invention relates to a slow release preparation of compound Repaglinide-metformin hydrochloride and a preparation method thereof, which mainly solve the problem of the synchronous slow release of insoluble medicament Repaglinide and water-soluble medicament metformin hydrochloride. The preparation method uses hydroxypropyl methylcellulose, glyceride behenate, ethylcellulose and the like as framework materials and comprises the steps of: respectively pelletizing the Repaglinide and the metformin hydrochloride, pressing into bilayer tablets or respectively pressing into small tablets, and encapsulating into capsules. The prepared compound slow release preparation not only can improve the curative effect based on the complementation between medicament action mechanisms and decrease the dose of each individual component to reduce toxic or side effects of the medicaments, cut also can slow down the release of the medicaments, stabilize the blood concentration, reduce the administration frequency, and improve the compliance of patients.