The litters (L) of the dominant species Cyclobalanopsis glauca and soil (S) under the virgin forest in the National Nature Reserve of Maolan karst area of Guizhou were used as the study materials. Biochars (BC400 and BC600) were made from L under 400 ℃ and 600 ℃, respectively. Four kinds of treatments were designed including S, S+L, S+BC400 and S+BC600 for a lab incubation (biochar 12.5 g/kg soil). Soil respiration, organic carbon (SOC), C/N ratio and pH were monitored dynamically during the incubation. The results showed that carbon net release rates of S+L, S+BC400 and S+BC600 increased by 34.98%, 42.45% and 9.83% compared with S in 180 d under 25 ℃, respectively, indicating the litters and biochars both significantly accelerated soil respiration (P<0.05). SOC content changes before and after incubation proved that BC400 promoted microbe transformation in SOC, but BC600 showed an inversive trend which can provide a reference for biochar applying for carbon sequestration in karst forest soil.