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.