Inclusion Criteria:  Patients who meet the World Health Organization (WHO) (1999) criteria for the diagnosis and classification criteria for type 2 diabetes mellitus; 18 ≤ age ≤ 75 years old, male or female; Body mass index (BMI) within the range of 19-35 kg/m^2 (inclusive), BMI = weight (kg) / height^2 (m^2); 7.0% ≤Hemoglobin A1c (HbA1c) ≤ 9.5%; Patients who voluntarily participate in the study and sign the informed consent form; Patients who agree to use contraception from the signing of the informed consent form until 1 month after the end of the last medication.  Exclusion Criteria:  Fasting plasma glucose (FPG) > 13.9 mmol/L; The investigator determines that the patients need to use insulin therapy; Patients with acute or serious complications of diabetes (including diabetic ketoacidosis, hyperosmotic nonketotic diabetic coma, lactic acidosis and hypoglycemia coma); History of severe hypoglycemia (hypoglycemia with severe cognitive impairment and requiring other measures to help recover); History of acute or chronic pancreatitis, or related diseases that are most common cause of acute pancreatitis (such as recurrent cholelithiasis, etc.); History of allergy to DPP-4 inhibitors or the investigator determines that the patients may be allergic to investigational drug; Patients with untreated hyperthyroidism and other diseases, which may affect blood glucose; Patients who have used other hypoglycemic drugs within 14 days before the first dose; or patients who are not suitable for this study as determined by the investigator due to taking other hypoglycemic drugs; Patients with inflammatory bowel disease, partial intestinal obstruction or chronic bowel disease related to obvious digestive and absorption disorders; Aspartate aminotransferase (AST) or Alanine aminotransferase (ALT) > 3 * upper limit of normal (ULN), or total bilirubin > 1.5 *ULN; Abnormal renal function: serum creatinine>1.5 * ULN; or eGFR< 45 mL/min/1.73m^2; White blood cells (WBC) < 3.0 *10^9/L and neutrophil count of peripheral blood < 1.5 * 10^9/L; hemoglobin < 100 g / L; triglyceride > 5.7 mmol/L; Patients who have the second or third degree atrioventricular block, long Q-T syndrome, or QTc>500 ms without cardiac pacemaker; Patients with any one of HBsAg, hepatitis C antibody, anti-HIV antibody and antibody of treponema pallidum positive; Female patients of childbearing age with pregnant test positive or lactating women; History of alcohol or drug abuse within 3 months before screening, alcohol abuse is average alcohol intake more than 14 units alcohol (1 unit=12 ounces or 360 mL of beer,1.5 ounces or 45 mL spirits with 40% alc/vol, 5 ounces or 150 mL grape wine); or intake any other products containing alcohol within 2 days before the first administration of investigational product; Patients who smoke more than 5 cigarettes per day within 3 months prior to screening; Patients with consumption of grapefruit juice, methylxanthine-rich food or beverage (such as coffee, tea, cola, chocolate, energy drinks) within 2 days before the first administration in treatment period , or patients who have strenuous exercise, or have other factors affecting drug absorption, distribution, metabolism, excretion, etc; Participation in other clinical trials or administration of any other investigational drugs or devices within 3 months before screening;  Patients with the following diseases:  Serious dysrhythmias, obvious left ventricular dysfunction, New York Heart Association (NYHA) functional class III or IV; History of unstable angina pectoris, myocardial infarction, or other high-risk coronary artery diseases; Uncontrolled hypertension, systolic pressure ≥160 mmHg or diastolic pressure ≥100 mmHg; History of cancer , organ transplantation; History of epilepsy, psychosis, severe depression, etc. Not suitable for this study as determined by the investigator due to other reasons.