Background: Alismatis rhizome (AR) is a popular traditional Chinese medicine, used for hyperlipidemia and diabetes in China for centuries; Alisma polysaccharides (AP) are the bioactive components in AR. This study investigates if glucose–lipid metabolism can be regulated by AP via miR-126 in vivo and in vitro. Materials and Methods: The diabetes group (diabetes mellitus) was injected intraperitoneally with streptozotocin (35 mg/kg) for 7 days. Diabetic mice treated with AP at an oral dose of either 400 mg/kg (high), 200 mg/kg (middle), or 100 mg/kg (low); and mice treated with pioglitazone (15 mg/kg) each day. The hypoglycemic and hypolipidemic effects of AP were demonstrated by measuring fasting blood glucose (FBG) levels, fasting insulin level, total cholesterol, triglyceride, low-density lipoprotein and high-density lipoprotein, observing insulin-sensitizing effects, and testing oral glucose tolerance. In addition, the expression of both miR-126 and related glucose–lipid genes in the primary hepatocytes was examined in diabetic mice. Results: The FBG, long-term blood glucose, and the ability to resolve blood glucose by insulin in AP groups were significantly better than that in model group. AP could reverse the expression level of miR-126 and genes. The addition of AP could reduce the effect of miR-126, reversing the expression of glucose–lipid genes in HepG2 cell. Conclusion: The results demonstrate that the expression of miR-126 can be directly decreased by AP in diabetic mice, especially in HepG2 cell, and AP also can ameliorate the glucose–lipid metabolism