In order to investigate relations between Robinia pseudocacia and environmental factors and find out the important influencing factors, we obtained data of growth of R. pseudocacia under three soil water conditions, that is favorable, medium drought and serious drought soil water condition, which respectively hold about 70%-80%, 50%-60% and 30%-40% of field water capacity and we also employ indicators from three levels —environmental factors, physical changes, and the growth situation to test and observe. The data was analyzed in a Hierarchical vector way. The results showed that the soil effective supplying water and temperature played important roles in this process. When the water content changed from favorable to medium drought or to serious drought, the influence of the environmental factors (including water, temperature etc.) on potentials leaf water and water use efficiency (WUE) was deepened gradually, but other physiology has no obvious changes. While photosynthetic rate, transpiration rate and WUE of R..pseudocacia were inhibited seriously. The total biomass of R.pseudocacia decreased remarkably. Water content of soil affects the survival and growth of R.pseudocacia obviously. In conclusion, the growth of R.pseudocacia has close relation to water content of soil, effective supplying water of soil and temperature etc. Therefore, our result approved reducing function hierarchical vector analysis is a reasonable method.