Time-space effect of soil nutrient and chemical characteristics of Robinia pseudoacia L.plantation forestland in Loess Plateau has been studied.The results shows that: soil organic matter,pH,total N,available N,available P and available K,exchangeable Ca and exchangeable base capacity changes irregularly with tree age,total P and exchangeable Mg changes fluctuantly;Soil organic matter,total N,available N decreases by power function with soil depth,available P tends to decreases,total P,available K,exchangeable Ca,exchangeable Mg and exchangeable base capacity varies irregularly with soil depth,but pH-value changes fluctuantly;Compared with wasteland,soil organic matter,total N,available N,total P,available P,exchangeable Ca,exchangeable Mg and exchangeable base capacity raises respectively by 21.56%~96.8%,34.3%~160.1%,191.5%~238.4%,2.1%~24.1%,19.82%~92.71%,64.21%~80.02%,25%~46.5%,67.2%~89.5%.These showed that Robinia pseudoacia L.plantation can improve the condition of soil nutrient effectively.