Abstract: In order to employ stripping urea melt to react with NaCl- to produce soda, the phase diagram of the Na+, NH4+/HCO3-, Cl-, (NH2)2CO-H2O system has been studied. In comparison with Na+, NH4+/HCO3-, Cl-, H2O system, the amout of water involved is much less for the urea saturated system. At the NaHCO3-NH4HCO3-NH4Cl saturated point, if there is no urea present, Na-uti-lization coefficient UNa = 83.1%. However, when saturated with urea, UNa= 85.80%. The NaHCO3 mother liquor contains 8.30 moles of water for one mole of NH4C1 in urea free system and contains 5.80 moles of water in urea saturated one. Therefore, 30% of H2O evaporation load would be saved for producing the same quatity of NH4Cl in urea saturated system. As urea wouldset out together with the ammonium chloride, consumption of steam for evaporation would be much less. For the purpose of separating the urea-NH4Cl compound fertilizer from the NaHCO3 mother liquor, it is necessary to investigate the phase diagram of the(NH2)2CO-NaCl-NH4Cl-H2O system at different temperatures.Experiments conducted show that at both 35℃ and 100℃, no double salts are formed, while at 25℃, solid phase of (NH2)2CO. NaCl. H2O is being observed. A NaHCO3-urea-NH4Cl production process is, thereby, being proposed, and a material balance calculation has been made. Theoretically speakly, with this process, for every ton of soda, produced 4.462 tons of urea-NH4Cl compound fertilizers may be produced simultaneously, and the fertilizer thus obtained contains 42.0%N, with 14% in NH4C1 included.