Planting tea is a typical way of land use of hillside fields in hilly regions of South Jiangsu Province.But the resultant soil erosion and its ecological impacts there should not be ignored.In order to measure soil erosion, the ¹³⁷Cs tracer method is a useful tool at present.However it is necessary to find out the background value of ¹³⁷Cs in the region and set up an applicable model for this method.After careful study the ¹³⁷Cs background value of the study area is 2 200 Bq m^-2 and a model for estimating erosion of cultivated soil is set up as h=Hc×(C_ref-C_t)/(C_ref-C_in).Based on the above work, the soil erosion rates are estimated and both direct and secondary ecological impacts of soil erosion are further discussed.The direct ecological impacts are thinning surface soil layers, deteriorating soil structure and decreasing soil nutrients.The secondary impacts include increase in fertilizer application and energy consumption, entrophication of waterbodies and change in landuse adaptability.In order to reveal seriousness of the damage of soil erosion to cultivated sloping fields in south Jiangsu Province by comparing with that in the Loess Plateau and red soil regions, an equivalent erosion module is put forward as index.