Abstract: 【Objective】This paper is aimed to explore the effects of the period of wetland reclamation on the property of soil profiles and changes of C and N content in Sanjiang plain, and to analyze their relationships systemically so as to provide foundations for land quality construction under local tillage way nowadays in this region.【Method】 Through investigation in the field, the changes of soil profiles layer, soil bulk density, and vegetation of wetlands with different period of tillage were conducted in northern Baoqing County and southeast Fuyuan County of Sanjiang plain. Surface and subsurface soil samples were collected, and C and N contents were detected and their changes with tillage years were analyzed. 【Result】Humus layer gradually became thinner while the soil layers became more apparent with the period of tillage lengthened, and there was a significantly negative relationship between them, and soil bulk density increased with the period of tillage prolonged just with a liner correlation. Whereas, the amount of organic carbon of surface and subsurface soil was reduced with the period of tillage lengthened, which could be described with the quadratic polynomial Y = b0 + b1x + b2x2. A significant negative relationship was also found between total nitrogen change in surface soil and the period of tillage, which could also be described with a quadratic polynomial. The C/N values of soils varied with the period of tillage changed, but they were affected by environmental conditions and had a degrading trend in recent years. Besides, the changes of organic carbon storage after wetland reclamation, and impact of growth environmental condition on wetland property, and wetland protection were all discussed in this study. 【Conclusion】There was an obvious degrading trend for organic matter and nitrogen content as well as thinner arable layer with tillage years prolonged. Therefore, it is necessary to increase applied amount of organic fertilizer and strengthen land nutrient management and improve cultivating type etc. in order to prohibit this condition and ensure sustainable and stable development of agriculture in this region.

Key words: Sanjiang plain, wetland, profiles, Organic matter, Total nitrogen