Abstract: 【Objection】In this study, the vertical zonal regularity with altitude and growth seasonal variation of the contents of soil dissolved organic carbon(DOC), microbial biomass carbon(MBC)and easily oxidized carbon(EOC)in the surface soil was investigated. The results provide a basis for the scientific evaluation of the stability of the soil carbon pool and the potential function of carbon sequestration in the original P. koraiensis forest, which is of great practical significance in the context of global climate change.【Method】We selected the original Pinus koraiensis-broadleaved mixed forest in Changbai Mountain(from 699 to 1 177 m)as a research object, and selected sample plots at 100 m intervals. At the same altitude, three sample plots were set, and a total of 10 sampling points with a size of 15 cm × 15 cm were randomly set up in an “S” shape at each plot. The contents of DOC, MBC and EOC in the surface soil(0-20 cm)were analyzed by using potassium sulfate extraction, chloroform fumigation extraction and potassium permanganate oxidation methods, respectively, to study the dynamic variations in altitude and growing seasons. 【Result】 We found the contents of DOC increased with altitude, the contents of EOC showed a trend of higher contents at altitudes of 699-1 044 m, although a lower content was observed at 1 177 m, and MBC exhibited the same pattern as EOC but in May and June. The three components accounted for 0.10%-1.45%, 0.08%-2.18% and 5.20%-69.18% of the TOC, respectively. Contents of the three active organic carbons and their proportions accounting for TOC changed obviously during the growing season(from May to October), with significant differences between months(P<0.05). The DOC content was higher in September, the MBC content was higher in June and September, and the EOC contents was the highest in May and June. The contents of all the three components were significantly correlated with available mineral nutrients(nitrogen, phosphorus, and potassium), pH, bulk density and water content of the soil samples(P<0.05), of which the correlation with water content was the highest(r = 0.835). 【Conclusion】The above results imply that the P. koraiensis forest at 699-818 m has a higher soil organic carbon pool stability and stronger soil carbon sink capacity. The accumulation of soil carbon mainly occurred in May, July, August and October, indicating a higher soil carbon sink capacity during this period. In general, the content of soil active organic carbon in the forest soil could be used as a sensitivity index to measure dynamic changes in forest soil nutrients(N, P and K).