Titanate modified bentonite could catalyze methane into synthesis carbon nanotubes at high temperature by thermal chemical vapor deposition. The element iron contained in bentonite acts as the catalytic metal of nanotubes. A conclusion was drawn that the quality and quantity of carbon nanotubes were best and largest respectively at 800 °C. If the temperature is higher than 900 °C,the quality of nanotubes would be bad. The catalytic capacity of modified bentonite would disappear below 700 °C. The catalyst is cheaper, and the treatment process of the catalyst is simpler than traditional metal catalyst , which may accelerate industrial synthesis of carbon nanotubes.