Four complexes with general formulas MIIL2·CH3OH (M = Co, Zn) and MIIL2 (M = Ni, Cu) were synthesized by transition metal ions MII (Co, Ni, Cu, Zn) reacting with 2-(2-hydroxyphenyl)benzimidazole (HL). Their thermal properties were studied; the probable thermal decomposition mechanism for the first step of the Co(II) and Zn(II) complexes was suggested, and the kinetic parameters were also given.