The objectives of this study are to understand the law of spatial and temporal changes in soil nutrient quality in the Taihu Lake valley during in period of past two decades, and reveal relationship the change in soil nutrient and its driving forces at a regional level over a long time. A long term sampling experiment was conducted to analyze changes in soil organic matter, total N, available N, available P, and available K in Ganlu Township, Wuxi City. Results show as follows: (i) Soil or ganic matter decreased in the first decade, then increased during the next decade, which is assumed to be related with tillage methods; (ii) Soil total N and available N steadily increased by about 114.4% and 104.7%, respect ively, after 20 years, which is supposed to be associated with the in creasing of the rate of nitrogen fertilizers. At percent, the application rate of nitrogen fertilizers is about 646kg hm^-2 a^-1, which is far beyond the absorption capacity of the crop for growth; and (iii) Soil available P and available K decreased by about 52.3% and 24.2%, respectively, during the period. The content of available P and available K in the soil was only 5.1 mg kg^-1 and 44.8mg kg^-1, respect ively, which is lower than the demand of the crop for normal growth. These changes are believed to a result of inadequate fertilizer input. Only 87. 0kg hm^-12 and 80.4kg hm^-2 were used in 1999. In a word, soil nutrient quality index (SNQI) decreased from 1981 to 1986, then increased after 1986. The analysis of the relationship between the changes of SNQI and the socio-economic factors revealed: (i) The impacts of state policies and tillage methods, cultivating systems on SNQI are very obvious; (ii) Agricultural net input is positively correlated with SNQI (r= 0.832, p< 0.05); and (iii) agricultural net income per hectare is negatively correlated with SNQI(r= 0.915; p< 0.05). Therefore, we can repay the variation of soil nutrient quality of the past and forecast changes in SNQI in future by long-term socio-economic statistics.