Abstract: The root growth and root activity of 1 a and 2 a Aegiceras corniculatum plants were compared to investigate the effect of plant age on the root growth characteristics. The results showed that, after 360 d of growth, the single plant biomass of 2 a plants Aegiceras corniculatum was 2.45 times that of the 1 a plants. The proportion of the root biomass to the whole plant biomass decreased with the increase of plant age. The annual increase of root number, root length and root diameter of 1 a plants were significantly larger than those of 2 a plants; the root water content showed a trend of first rising then declining; the 2 a plants had relatively more stable root activity than the 1 a plants. Overall, significant differences existed between different ages of Aegiceras corniculatum in the root growth and activity.