Abstract: Myrica rubra is not only a subtropical tree but also a Actinomycete-nodulated plant. Root nodules of Myrica rubra have a nitrogen-fixing activity. The nitrogenase activity of exised nodules can last 4-5 hours and keep a higher activity. The nitrogen-fixing activities of nodules were determined separately, the highest activity was found in the matured nodules. The optimum temperature for nitrogen fixation of exised nodules ranged 25-30℃, the highest is at 30℃ Both nitrogenase activity of the seedlings with root nodules and nitrate reductase activity (NRA) in seedling leaves are inhibited by NO3-. However, the inhibition of NRA in the plants with or without nodules has a certain difference. The root nodules of Myrica rubra contain a hydrogen-absorbing enzyme which can increase effectively nitrogenase activity.