Bloedite (Na 2 SO 4 •MgSO 4 •4H 2 O) is an important natural chemical resource. So far, it has not been developed and utilized effectively because of its separation difficulties. To develop a new technology to produce Na 2 SO 4 and Mg−N compound fertilizers by a CO(NH 2 ) 2 salting-out method to separate bloedite, the mutual solubilities of the ternary system Na 2 SO 4 −CO(NH 2 ) 2 −H 2 O and the quaternary system Na 2 SO 4 −MgSO 4 −CO(NH 2 ) 2 −H 2 O at 25 °C were measured, and the phase digrams of these two systems were investigated. According to the phase diagram analysis, it indicates that, by using the CO(NH 2 ) 2 salting-out method, Na 2 SO 4 and MgSO 4 in bloedite can achieve better separation and anhydrous sodium sulfate can be directly obtained. The yield of Na 2 SO 4 was 90.98 % in the case of the mother solution without cycling and utilizing. Adding a certain amount of CO(NH 2 ) 2 into the mother solution after Na 2 SO 4 separation, MgSO 4 •CO(NH 2 ) 2 •2H 2 O can be obtained. After separating MgSO 4 •CO(NH 2 ) 2 •2H 2 O from the solution, the remain mother solution was recycled to dissolve bloedite. The new technology can get stable recycle production.