Abstract: The influence of carbon content, temperature, time, particle size and from of samples on the reduction of SiO₂ by carbon in zircon were studied. The effects of these factors on the ratio of desilica from zircon were obtained. The maximum value of this ratio could reach to 97.22% theoritically. The apparent activation energy for the reaction of zircon with carbon was 282.04 kJ/mol (1600~2000℃).Besides, the limiting step of reduction of SiO₂ in zircon was the heat decomposition of zircon, not the reaction of SiO₂ with carbon after decompostion of zircon.