The genetic diversity and structure of nine natural populations of Horsfieldia hainanensis Merr., an endangered plant endemic to China, were studied using inter-simple sequence repeat markers. Nine primers were selected from 100 primers to evaluate 126 individual plants, from which a total of 136 bands were amplified and 108 bands were polymorphic. Our results demonstrated that the genetic diversity level of H. hainanensis was high with a percentage of polymorphic bands, Shannon's diversity index and Nei's genetic diversity index at the species...