Abstract: The stability constants of ternary mixed ligand coordination compounds formed from some amino-acids (serine, valine, alanine and α-amino-isobutyric) and 1,10-phenanthroline with Cu(Ⅱ) were determined by pH-meterically at 25±0.1℃, 35±0.1℃ and 45±0.1℃ in the presence of 0.16M KNO₃Linear relationships not only exist between the stability of ternary mixed ligand coordination compound and the base strength of ligands but also exist between the formation enthalpy of coordination compounds and the protonalion enthalpy of the ligands and between the formation entropy of coordination compounds and the protonation entropy of the ligands as well.