Based on collected samples in 2011, by referring the data in the 2nd national soil survey in 1981, this paper evaluated the temporal and spatial variability of soil organic matter (SOM) and total nitrogen (STN) in farmlands during the past 30 years in Shuyang County, Jiangsu Province and further discussed natural and anthropic factors leading to the variability. The results showed that, in the past 30 years, SOM and STN in topsoil (0-20 cm) significantly increased. The contents of SOM and STN in 2011 were 23.12 g/kg and 1.36 g/kg, respectively, 12.15 g/kg and 0.61 g/kg higher than those in 1981, the increasing rates were 0.41 g/(kg·a) and 0.02 g/(kg·a) for SOM and STN. In spatial, the SOM and STN in 2011 had the similar spatial distributions to those in 1981, showing that clayey soil in the north area had higher contents than sandy soil in the south area, and paddy fields in the east area had higher contents than dry fields in the west area. Soil texture was main natural structural factor affecting this temporal and spatial variability, while the increase of crop-residue incorporation and the transformation of land-use patterns were major anthropic random factors affecting them in the past 30 years.