The study on the relationship between plant species diversity and soil factors in the bird island of Qinghai Lake indicated that this island was a low diversity district, its Shannon-Wienner index and species richness decreased with the increasing soil available K, water soluble salt concentration and pH, and there were significant linear and quadratic correlations between them. Stepwise linear regressions showed that soil available K and water soluble salt were the key factors to estimate Shannon-Wienner index and species richness in this island, respectively, and no correlation was found between species evenness and soil factors.