By taking wetland and natural forest land as CK, paddy fields and drylands of different cultivated years in Sanjiang Plain were studied. Soil samples were collected according to profile layers, and soil organic carbon (SOC) content, pH value and total nitrogen concentration were measured and analyzed statistically by SPSS software, Vertical distribution of SOC content and relationships with pH value as well as with total nitrogen content were explored. Results showed that vertical distribution of SOC content varies with soil depth and land use type; Comparing with the wetland (CK), SOC contents in surface layers of paddy soils cultivated for 10 and 25 years decreased by 49.3% (P<0.01) and 14.3% (P<0.05), respectively; Comparing with natural forest soil (CK), SOC contents in surface layers of drylands cultivated for 5 and 18 years decreased by 81.9% (P<0.01) and 68.3% (P<0.01), respectively; SOC contents of natural forest land and drylands cultivated for 18 years both had significantly negative correlations with pH values, correlation coefficients were -0.578 (P<0.05) and -0.965 (P<0.01), respectively; There were significant correlations between SOC and total nitrogen contents of studied land use types, correlation coefficients were all above 0.580 (P<0.05).