This is a prospective, multi-center, randomized, open-label, parallel-arm controlled study, for which a total of 216 patients with type 2 diabetic nephropathy (Stage II-IV) will be enrolled. The subjects will be randomized to three groups in 1:1:1 ratio. One group receive Alfacalcidol 0.25ug/day and Irbesartan 150mg/day for 16 consecutive weeks. The second group receive Alfacalcidol 0.25ug/day alone for 16 consecutive weeks. The third group receive Irbesartan 150mg/day alone for 16 consecutive weeks. All subjects will be followed up for 4 weeks after medication is over. A total of 4 visits have been scheduled for this study at week 0, week 8, week 16, week 20.

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.