Abstract: We analyze the source and effect factors of CO₂ in Butuo, Sichuan Province, basing on observed data from January 2005 to August 2013. The results show that CO₂ comes mainly from soil respiration, and the variation features are mainly affected by soil temperature and moisture. In detail, the variation features of the CO₂ have the same rhythm with the biological growth equation, so we conclude that it comes mainly from soil respiration. The variation features of the CO₂ are mainly affected by soil temperature in November each year to the next March, and during this time the values of CO₂ are proportional to the soil temperature. The variation features of the CO₂ are mainly affected by soil moisture in April each year to October, and during this time the values of CO₂ are proportional to the soil moisture. The values of the CO₂ in the middle year of 2007, 2012 and 2013 are higher than other years, it is for the reason that the cumulative rainfall in these years are much bigger, leading to bigger soil moisture and respiration. Therefore, it has no rela tionship with earthquake preparation or tectonic activity.

Key words: CO₂ Variation, Soil respiration, Tectonic activity