Treatment by ascertaining the causes are the important therapeutic principle of Chinese medicine. Its essence is searching for the primary cause of disease in treatment and treatment by ascertaining the pathogeny. At present

Chinese medical etiology is too broad

obscure and lack of pertinence.

Discussing about diabetic nephropathy from ascertaining causes of disease

syndrome and symptom could increase the practicability and pertinence of clinical treatment. This article put forward that diabetes with Yin deficiency is the pathologic basis of diabetic nephropathy. This pathogeny caused and decided the pathogenesis progress of diabetic nephropathy. It is different from pathogenesis characteristics of the other kidney disease. Ascertaining the cause of syndrome about diabetic nephropathy is to find out the recessive cause of the present syndrome. Ascertaining the cause of symptom is the guarantee to improve the clinical symptoms.