Temperature effects on the fluorescence emission spectra of 0.01 M Eu(III) ion with ClO$_4$, Cl$^-$, NO$_3$ were studied. Relative intensity change of hypersensitive band ($^5D0; { o};^7F_2$) and nonhypersensitive band ($^5D0 ;{ o};^7F_1$) was quite remarkable with temperature and ligand. The relative intensity change was interpreted as the change of formation constant and used to calculation the enthalpy change of $Eu(H_2O)_X^{3+}$+ to EuL(H$_2O)_{X-1}^{2+}$ complex. $Delta{H}$ of $Eu(H_2O)_X^{3+}$ to EuCl(H$_2O)_{X-1}^{2+}$ was roughly 15 kJ/mol and temperature independent, but $Delta{H}$ of EuNO$_3(H_2O)_{X-1}^{2+}$ was changed with temperature; -11 kJ/mol at 25$^{circ}C$ and 47 kJ/mol at 250$^{circ}C$.