Melamine has been the main factor leading to infant urinary calculi occurring on a rather wide scale in China in 2008, which were the results of a rapid aggradation of metabolites such as cyanuric acid diamide, cyanuric acid, etc., causing uric acid stone to accumulate. Here, we present a report on 24 infants who were admitted to our department, their ages ranging from 3 to 10 months. All of these infants had a confirmed history of having been fed with the “Sanlu” brand milk powder, which contained excessive levels of melamine, with the highest being 2,563 mg/kg. The diagnosis, medical treatment and follow-up by ultrasonography at 1, 3, 6, 12 months were reported. 22 cases of these infants were rehabilitated after medical treatment and 1 infant underwent pyelolithotomy for relieving an obvious ureter obstruction. No recurrence was found in these babies thereafter. Another infant died from rapidly worsening renal failure. Therefore, this series of cases have demonstrated that melamine contained in the “Sanlu” milk powder was the main cause of these urinary stones. Urine alkalinization and stone liberalization were the most effective treatments. Fast diagnosis and treatment of acute obstructive urolithiasis may prevent the development of acute renal failure, which is associated with high morbidity and mortality rates.