In this paper FeSO4 ZnSO4 H2O water system is studied by isothermal dissolution equilibrium method Zn2+and Fe2+concentration were used as axes in the Cartesian coordinates,FeSO4 ZnSO4 H2O system phase diagram under 0℃,10℃ and 25℃,are made. In the phase diagram,the single phase region and above the line of c(Fe2+)+c(Zn2+)=100 g/L overlap region is Zn Fe regional recipes of trace elements soluble fertilizer formulations.The results of multi temperature phase diagram analyzing showed that for the treatment of Zn Fe multi temperature phase diagram under 10℃,liquid fertilizer have good storage performance.