Carbon storage is a kind of wetland ecosystem service,which provides support and protection for economic activities by mitigating global climate change.There is a large area of wetlands developed in the Sanjiang Plain,which is located at the northeast corner of Heilongjiang Province in China.Wetland soils in the Sanjiang Plain,including peat soil,marsh soil,meadow soil and albic soil,are an important soil organic carbon pool,with a stock of 6.21×108t organic carbon.The wetlands area in the Sanjiang plain was about 534×104ha in 1949,however more than 70% of the wetlands have been lost due to large scale reclamation.Huge amount of CO2 produced by decomposition of organic matter in soils released to the atmosphere as a result of draining of water from wetlands.With the increase of cropland area,the organic carbon storage in wetland soils in the Sanjiang Plain decreased by about 3/4 of that in 1950 due to wetland loss and degradation,soil loss and irrational farming practices. This paper estimates the value of carbon storage in wetland soils in the Sanjiang Plain based on the storage and fluctuation of wetland soil carbon in recent 50 years.The result will be used to analyze the effects of agricultural development on carbon storage in wetland soils,and to support policy making for wetland protection and global climate change.It seeks to build a classification system for wetland carbon storage valuation techniques.The value of wetland carbon storage is evaluated based on market price,cost or results of investigation.The basic principle,suitability and limitations of valuation techniques including Damage Valuation Method,Alternative Cost of Abatement Method,Market Price Method are analyzes,Shadow Price Method,Substitute Cost Method and Replacement/Restoration Cost Method.Different valuation methods result in different unit values of carbon storage. The theoretical reasonability,feasibility of methodology,existing reality and local level suitability of valuation techniques,are compares aiming at finding out a rational range of unit value of wetland carbon storage.The results show that the first choice should be the Market Price Method,complemented by the other methods.The unit value of carbon storage ranges from US$5/tC to US$25/tC.The lowest value is estimated by the Market Price Method,and the highest value is the mean of the result of the Damage Valuation Method,the Alternative Cost of Abatement Method,the Shadow Price Method and Substitute Cost Method.The total value of carbon storage in wetland soil in the Sanjiang Plain amounts to US$3.10 billion-US$15.52 billion.The total carbon loss value caused by reclamation amounts to US$1.08 billion-US$5.38 billion,and the average annual carbon loss value is US$4.3/ha-US$21.5/ha.