A series of the carbon nanotubes were synthesized on quartz substrates in a chemical vapor deposition (CVD) process. Ethylene was used as the carbon source, and ferrocene used as the catalyst. The scanning electron microscope (SEM) and Raman spectrum were employed to investigate the effects of reaction temperature on the structure and components of the carbon nanotubes. The results showed that, when the reaction temperature is 860°C , the best synthesis of the well-distributed carbon nanotubes with less of non-carbon impurity was achieved. At this condition, The length of the CNTs was 95 μm and the diameter was 104 nm.