Dissolved organic matter (DOM) is one of the main carbon and nutrient pools in the forest ecosystem. Its effect on carbon sequestration in forest soil has received great attention. However, the influence of DOM on the organic carbon mineralization in forest soil is still unclear. Here, a short-term (36 h) incubation experiment was conducted to measure δ¹³C within soil CO₂ efflux following soil priming effects caused by the addition of DOM from leaf and root litter of Castanopsis carlesii and Cunninghamia lanceolata. The results showed that CO₂ efflux from Castanopsis carlesii leaf litter DOM and Cunninghamia lanceolata leaf litter DOM peaked at 12 h, being 8.0 and 3.4 times higher than that at 2 h, and 4.6 and 7.0 times higher than that at 36 h, respectively. The CO₂ efflux from soil organic carbon (SOC) was also highest at 12 h and was 10.1 and 6.3 times higher than that in the control. The use of ¹³C-labeled DOM additions allowed the total respired CO₂ to be distinguished into that derived from the added DOM and that from SOC mineralization. The cumulative CO₂ emission from added litter DOM was significantly greater than that from the added root litter DOM. In addition, the cumulative emission of CO₂ from Castanopsis carlesii leaf litter DOM was significantly greater than that from Cunninghamia lanceolata leaf litter DOM. There was a significant positive relationship between soil CO₂ efflux and the content of dissolved organic carbon. DOM from different sources had different priming effects (PEs) on SOC mineralization. During the 36 h of incubation, soils amended with leaf litter DOM always had a higher PE than those amended with root litter DOM. At 5 h, for all soils amended with DOM, the PE reached the peak. At 36 h, soil amended with Cunninghamia lanceolata root litter DOM changed from positive to negative PE. The microbial mechanisms of the priming effects of DOM inputs on SOC mineralization will be studied in future.