Objective:To explore the effective parts of Alisma orientalis(Samuel.) Juzep. associated with blood glucose decrease in type 2 diabetic mice. MethodsEthanol extracts from A. orientalis were obtained by ultrasonic extraction. Then, the ethanol extract was extracted and separated with petroleum ether, ethyl acetate, water saturated n-butanol and water respectively. After decompressing concentration, these solvent extractions were applied to type 2 diabetic mice model induced by intraperitoneal injection of streptozotocin and nicotine. After successful modeling,the mice were divided into the blank control group(without injection of streptozotocin and nicotine),model group of type 2 diabetes mellitus,positive control group and test drug groups,8 in each group. The blank control group and model group were treated with 0.9% NaCl at the dose of 10μl/g,the test drug groups were treated with corresponding extracts from different solvent extractions described above at the high-,mid-,low-dose of 100,50,25 μg/g respectively. The positive control group was treated with rosiglitazone at the dose of 10μg/g. The treatment course was 21 days for intragastric administration. The effective parts of Alisma orientalis(Samuel.) Juzep. associated with blood glucose decrease in type 2 diabetic mice were screened and then the effect of the screened effective part on the differentiation of 3T3-L1 pre-adipocyte was observed.  Results:Compared with the model group,the blood glucose was decreased after the intragastric administration with ethyl acetate extract of A. orientalis at dose of 100μg/g for 21 days and the glucose tolerance during the oral glucose tolerance test (OGTT) was improved(P<0. 01). The differentiation of pre-adipocyte was promoted when the ethyl acetate extract of A. orientalis at the concentration of 1 mg/L and 10 mg/L.  Conclusion:The ethyl acetate extract of A. orientalis reduced the blood glucose in type 2 diabetic mice and promoted the differentiation of 3T3-L1 pre-adipocytes, but the specific mechanism still need to be further studied.