Dissolved organic matter (DOM) as an important source of soil dissolved organic carbon, it affects soil mineralization through changes of soil microbial quantity and activity. However, many reports about the DOM impact on soil microbial respiration and quotient focused on surface soil, its effect on deep soil is less paid attention. A 120-day incubation experiment was done to reveal the effects of DOM from Castanopsis carlesii fresh leaf on soil microbial respiration and quotient values of surface soil (0-10 cm) and deep soil (40-60 cm) in a secondary Castanopsis carlesii forest. It will provide some knowledge about the role of DOM input on soil C process in subtropical forests. The results showed that on the first day, instantaneous CO₂ emission rates of surface and deep soils after DOM addition were significantly higher than those in control treatments (P < 0.001), being 3.58 and 6.93 times of the control, respectively, but after that CO₂ emission rates reduced significantly. In DOM added treatment or control, the cumulative CO₂ emission in surface soil was significantly greater than that in the deep soil. After adding DOM, the cumulative CO₂ emissions from surface soil was significantly higher than from the control (P < 0.001). However, no obvious difference for the cumulative CO₂ emission from deep soil between DOM addition and control treatments was found. Microbial biomass C (MBC) content of surface soil during the incubation period was significantly greater than that in deep soil. The MBC content in surface soil under DOM addition treatment was higher than that in control treatment during the incubation period. The same trend was for the deep soil except for the third day. Under DOM addition treatment, soil organic C contents in surface and deep soils on the 120th day were 26% and 19% less than those on the third day, respectively. At the end of incubation, the soil metabolic quotient (qCO₂) in DOM added deep soil was significantly lower than those in deep soil of the control and DOM added surface soil (P < 0.001), indicating the increase of carbon use efficiency after DOM addition into deep soil. After incubation for 120 days, microbial quotient of DOM added deep soil was 1.58 times than that of the initial period (the 3rd day). In contrast, soil microbial quotients of surface soil under DOM added treatment and surface and deep soils of control treatment were 68%, 79% and 21% on the 3rd day, respectively. This showed that DOM addition was beneficial for the improvement of the quality of deep soil.