Abstract: Biochar addition to soil has been widely accepted as a soil conditioner to improve soil physical and biochemical properties, increase crop yields and enhance fertilizer use efficiency. However, there has always been a dispute about whether biochar inhibits soil respiration. Five levels of branches-derived biochar from apple tree (0, 20, 40, 60 and 80 t/hm²) were used. The effects of biochar on ecosystem respiration (R_e), soil respiration (R_s), plant respiration (R_p), total soil organic carbon (TOC), soil particulate organic carbon (POC), soil active organic carbon (AOC) and water-soluble organic carbon (WSOC) were investigated in a plot trial. The results showed that, compared to the control treatment, ecosystem respiration, soil respiration and plant respiration were increased by 9.98%-27.57%, 9.33%-19.47% and 10.18%-30.14%, respectively. Soil respiration was higher at biochar levels of 20 and 40 t/hm² than that in the biochar levels of 60 and 80 t/hm², while ecosystem respiration and plant respiration reached the maximum at 40 t/hm². Biochar amendment significantly increased the contents of TOC, POC and AOC in the 0-20 cm soil layer, and the contents of TOC and POC were positively correlated with the biochar dosage. The contents of WSOC significantly decreased at biochar levels of 60 and 80 t/hm², and it decreased respectively by 21.82%-28.37%, 35.88%-36.58% and 32.28%-44.07% in 0-10, >10-20 and >20-30 cm soil layers compared to the control. The results indicated that as a long-term mechanism of carbon sequestration, biochar improved the total soil organic carbon. In addition, soil respiration could be improved by biochar amendment.