It has been known that a low-protein diet can slow down the progression of chronic kidney disease, while the dietary modification in diabetic kidney disease is more comlex, and the effect of protein restriction is still controversial. Besides, protein is one of the three major nutrients for building the body and providing calories, and low protein diet may also increase the risk of malnutrition, The optimal amount of protein intake in diabetic kidney disease is undefined yet. Besides, the role of ketoanalogue in diabetic nephropathy is also undetermined; this article attempts to discuss the mechanism and evidence of low protein diet in diabetic kidney disease and provide clinical suggestion.