The purpose of this study is to obtain information on efficacy and safety of SHR3824 with metformin over 24 weeks and 52 weeks in metformin monotherapy poorly glycemic controlled chinese Type 2 Diabetes. Efficacy and safety will be evaluated by comparing the effect of SHR3824 with metformin to placebo with metformin when given in oral doses.

A phase III clinical study on efficacy and safety of SHR3824 combined with metformin for type 2 diabetes with poor glucose control in metformin monotherapy (multicenter, randomized, double-blind, placebo-parallel control). The 450 subjects received at least eight weeks of metformin monotherapy at a steady dose of 1500 mg or more before screening.

Evaluation of efficacy: compared with the group of placebo combined with metformin, HbA1c, fasting plasma glucose, postprandial plasma glucose, fasting body weight and blood pressure changes in the SHR3824 with metformin group

Inclusion Criteria:

• Patients must have a diagnosis of type 2 diabetes mellitus;
• Patients with type 2 diabetes mellitus treated with metformin monotherapy for ≥ 8 weeks and poor glycemic control, metformin dose stabilized ≥1500mg / day;
• FPG<=15mmol/L;
• Hemoglobin A1c levels >=7.0% and <=10.5%;
• Body mass index (BMI) 19 to 35 kg/m2;

Exclusion Criteria:

• Type I diabetes mellitus, diabetes mellitus resulting from pancreatic disorder, or secondary diabetes mellitus (acromegaly, Cushing's syndrome, etc.);
• Past or current history of severe diabetic complications (proliferative diabetic retinopathy, stage III or later stage overt nephropathy, diabetic ketoacidosis, or serious diabetic neuropathy);
• Systolic blood pressure of ≥160 mmHg or diastolic blood pressure of ≥100 mmHg on the start or end day of the run-in period;
• History of myocardial infarction, unstable angina, or cerebrovascular disorder within 6 months before the start of the run-in period;
• Past or current history of malignant tumor;
• Past or current history of drug hypersensitivity such as shock and anaphylactoid symptoms;
• Pregnant women, lactating mothers, or women of childbearing potential;
• Any condition that subjects are assessed to be ineligible by the investigator (sub investigator).