The effective separation of K3VO4 and K2CO3 from KOH-K2CO3-K3VO4-H2O system plays an important role in a new vanadium production process developed by the Institute of Process Engineering, Chinese Academy of Sciences. In order to design an effective separation strategy, the dissolution behavior of K3VO4 and K2CO3 in KOH-K2CO3-K3VO4-H2O system at (313.15 and 353.15) K was investigated, and the solubility isotherms were plotted. In addition, the solubility of K3VO4 in KOH solutions was compared with that in K2CO3 saturated KOH solutions, and the solubility of K2CO3 in KOH solutions was also compared with that in K3VO4 saturated KOH solutions. From the solubility data analysis, a method of first separation K2CO3 via cooling crystallization followed by separation K3VO4 via cooling crystallization in the concentrated alkaline solution was proposed.