Abstract: The rams which haven＇t been castrated were fed with mixture dietary of high dosage of phosphate and magnesium contents under free water intake condition. After one month of feeding, the control group appeared normal and occurred irrelevant urinary calculi symptoms, whereas high serum magnesium and phosphorous levels were present in the experimental group. Crystallographic analysis of urinary sediments shows same morphology as guanite. Urinary calculi that consist of phosphate and magnesium were observed by anatomic study of anuria rams. It is revealed that mixture dietary of high dosage of phosphate and magnesium contents is the potential cause of ram urinary calculi, stone formation is related to the higher phosphate and magnesium contents in dietary.