Clinical Study of Treating Type 2 Diabetic Nephropathy With Alfacalcidol and Irbesartan

Inclusion Criteria: * Adult Chinese subjects, at age 18-65, diagnosed with Type 2 diabetic nephropathy (Stage II-IV) who meet the WHO diagnostic standards of diabetes in 1999. The international Mogensen staging standard for diabetic nephropathy is used. Specifically, in Stage II (normal albuminuria stage), the UAER is normal (\<20μg /min or\<30mg/24h). In Stage III (early diabetic nephropathy stage), the UAER is 20-200μg /min or 30-300 mg/24h. In Stage IV (clinical or overt diabetic nephropathy stage), the UAER is \>200μg/min or urine protein quantitation is \>500mg /24h. Exclusion Criteria: * Renal damage caused by other causes; * Uncontrolled hypertension (blood pressure constantly greater than 140/ 90mmHg); * Type 1 Diabetes * Any acute and chronic infections; * Glycosylated hemoglobin (HbA1c)\>7.5%; * 24h urinary protein quantity\>3g, serum albumin\<25g /L and estimated glomerular filtration rate (eGFR)\<60 ml/min; * Patients who suffered from malignant tumors or any illness that endanger life, such as liver, kidney, heart and lung function insufficiency over the past 5 years; * People who have received the gastrointestinal operation, which may affect absorption of Vitamin D; * People who have taken such drugs as angiotensin receptor blocker, calcium, and angiotensin converting enzyme inhibitor that affect excretion of urine protein, and who have been allergic to Vitamin D; * Pregnant or lactating women; * Other candidates that are deemed not suitable by investigators.