Nanometer cobalt ferrite (Co) was synthesized by polyol-medium solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Further, the catalytic activity and kinetic parameters of Co nanocrystallites on the thermal decomposition behavior of ammonium perchlorate (AP) have been investigated by thermogravimetry and differential scanning calorimetry analysis (TG-DSC). The results imply that the catalytic performance of Co nanocrystallites is significant and the decrease in the activation energy and the increase in the rate constant for AP further confirm the enhancement in catalytic activity of Co nanocrystallites. A mechanism based on an proton transfer process has also been proposed for AP in the presence of Co nanocrystallites.