Abstract: Nyssa yunnanensis is a critically endangered species in China,with only 8 wild populations left in Yunnan. In order to study the causes of endangerment and make effective protection, both methods of in-situ experiment in field and manipulated greenhouse experiments were used to examine whether N. yunnanensis had autotoxic effects on seed germination and seedling growth. The results demonstrated that the seed germination of N. yunnanensis was significantly inhibited by the litter in the field and its seed capsule. Also, different organs of N. yunnanensis aqueous extract have significant negative effects on seeds germination, among which the inhibition rate of root aqueous extracts (80.90%) was significantly higher than that of other parts' aqueous extracts. Furthermore, the seedling growth (shoot height, number of leaves and biomass) of N. yunnanensis was suppressed by aqueous extracts of different organs of itself. And seedling growth was significantly poorer on the soil where N. yunnanensis had previously grown than on the soils where N. sinensis had previously grown or no plants had grown. The results are consistent with the hypothesis that N. yunnanensis negatively affects its natural regeneration through autotoxicity.