The title complex,formulated as Co(tda)(5-mphen)(H2O)(H2tda=thiodiglycolic acid,5-mphen=5-methyl-1,10-phenanthroline),was synthesized and characterized by elemental analysis,IR spectroscopy,X-ray sin-gle crystal diffraction,and TG-DTG techniques. The complex crystallized in monoclinic space group C2/c,with parameters of a=1.8142(2) nm,b=0.78251(9) nm,c=2.4624(3) nm,β=93.809(2)°,V=3.4880(7) nm3,Z=8,Dc=1.579 g/cm3,the final R indices[I>2σ(I)] are R1=0.0469,wR2=0.1021,R indices for all data are R1=0.0835,wR2=0.1169. The central Co2+ cation is coordinated in a distorted octahedral geometry with the ligand tda,5-mphen,and water mole-cule. The coordination complex possesses a three-dimensional framework by means of hydrogen bonds and π-π stacking interactions. According to TG-DTG curves,the possible thermal decomposition mechanisms,the possible kinetic parameters,and equation of dehydration stage of the complex are obtained,that is,Ea=110.98 kJ/mol,lg(A/s-1)=8.554,dα/dT = 108.5546/β·3(1-α)[-ln(1-α)]2/3·exp(-13349/T),respectively.