Homogeneous carbon nanoparticles were synthesized by chemical vapor deposition (CVD) from acetylene with zeolite as template in an atmosphere of argon. The microstructure of the products was characterized by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the as-synthesized products were quasi-spherical carbon nanoparticles with diameter of ca.150 nm and the interplanar distance of 0.3477 nm, and their purity was above 90%. The thermal stability of carbon nanoparticles was relatively stable. They can maintain their structure over 600°C in air or over 1000°C in argon atmosphere. In addition the formation mechanism of carbon nanoparticles was discussed briefly. Carbon source firstly filled into the template, then pyrolyzed and finally took the form of the product in consequence of template deformation.