Abstract: The work cells introducing LaF3 single crystal (mixed) as solid electrolyte was prepared using Pb-PbF2 reference electrode, Sn-SnF2 work electrode and Ag electrode wire by means of grinding, sieving and mixing Pb, PbF2, Sn and SnF2 together and pressing them into thin piece in a ratio of 4:1. The whole operating process was done in a box filled in with Ar gas. Its composition is (+)Ag|Pb,PbF2|LaF3 single crystal (mixed) |Sn,SnF2|Ag(-). The EMF (electromotive force) of cell was measured in the temperature rang from 293.15 K to 353.15 K. The relationship between SnF2 standard Gibbs free energy of formation and temperature was calculated on the basis of two kinds of PbF2 standard Gibbs free energy of formation. Because the EMF measuring errors are far smaller than that of PbF2 Gibbs free energy and the difference between two expressions of SnF2 standard Gibbs free energy of formation is very small, both the calculated results as above are confirmed reliable.