The inducing effect of potassium citrate (K3cit) on simultaneous growth of calcium oxalate mono-(COM), di-(COD), and trihydrate (COT) crystals in synthetic urine was observed with double diffusion gelatinous technique. K3cit can induce the formation of COD and COT,inhibit the aggregation and decrease the surface area of COM crystals. It supported the clinical use of K3cit and may provide important clues to this disease in cure and in search for new drugs.