Abstract: Thermotropic phase transitions in the perovskite-type layer compounds n-(C₁₂H₂₅NH₃)₂MnCl₄ and n-(C₁₄H₂₉NH₃)₂MnCl₄ were synthesized and a series of their mixtures were prepared from ethanol solution. The nonisothermal kinetics of solid-solid phase transitions in C₁₂Mn, C₁₄Mn and their binary system was investigated by DSC. Kissinger and Ozawa methods were applied to determine the activation energy and reaction order of the solid-solid transitions, and the results of two methods are coincident. The value of activation energy Ea showed fluctuant with increasing X_C12Mn. The reaction order of C_nZn and their binary system is about 1.