The invention provides a metformin hydrochloride / voglibose sugar-lowering oral preparation composition and a preparation method thereof. The weight ratio of two main medicines is 8000:1-375:1, preferably 2500:1-625:1. Except for the main medicines, the composition also can further contain commonly used medicine accessories, such as a binder, a filling agent, a disintegrating agent, a lubricant, a flavoring agent, a wetting agent and a flow agent, and the obtained composition can be prepared into tablets, granules, soft and hard capsules, sustained and controlled release preparations, optimum enteric-coated tablets, enteric-coated granules and enteric-coated soft and hard capsules by conventional methods. The composition provided by the invention has action mechanism complementation of the main medicines, multiple target points, good compliance of patients, and the like. The sugar-lowering oral preparation composition can be used for the first-line therapy of type 2 diabetes, or can be used for second-line therapy under the condition that the metformin hydrochloride or sulfonylurea medicines fail to singly and effectively control blood sugar; and the sugar-lowering oral preparation composition is especially suitable for the therapy of diabetic patients suffering from latent autoimmune diabetes in adults (LADA) and hyperinsulinemia.