Laboratory study on NHNH₄⁺-N release from the sediments of the West Lake in Hangzhou was conducted under anaerobic conditions using Rhizon-SMS (Rhizon Soil Moisture Sampler) and homemade incubator. Three phases were observed in the cumulative NH₄⁺-N flux versus time curve and NH₄⁺-N release rates calculated from two linear parts of flux-time curve were 11.60 and 5.12 mg m^-2d^-1, respectively.Rhizon-SMS was found to be easy to operate and characterized by high spatial and terporal resolution. Therefore, it has the potential of serving as a powerful tool inpore water geochemistry studies.