Abstract: Effect of biochar addition on soil CO₂ efflux in a typical Chinese chestnut (Castanea mollissima) plantation in Lin’an, Zhejiang Province, China was investigated from July 2012 to July 2013 by the static closed chamberGC technique. Soil temperature, soil moisture, WSOC and MBC concentrations were determined as well. Results showed that soil CO₂ efflux exhibited a strong seasonal pattern. Compared with the control (without biochar application), the biochar treatment increased the soil CO₂ efflux only in the first month since application, and then the effect diminished thereafter. There were no significant differences in the annual cumulative value of soil CO₂ efflux between the biochar and control treatments. The annual mean value in soil MBC concentration (362 mg·kg^-1) in the biochar treatment was higher than that (322 mg·kg^-1) in the control. However, no significant difference in the soil WSOC concentration was found between the biochar and control treatments. Strong exponential relationships between soil temperature and soil CO₂ efflux were observed regardless of the treatment and soil layer. The apparent temperature sensitivity (Q₁₀) of soil CO₂ efflux in the biochar treatment was higher than that in the control. Soil CO₂ efflux was related to soil WSOC concentration but not with soil MBC or moisture content. To conclude, the application of bamboo leaf biochar did not affect the annual cumulative CO₂ emission in the Chinese chestnut plantation but increased the Q₁₀, and the CO₂ efflux was predominantly controlled by the soil temperature and soil WSOC level.