Abstract: Brachionus plicatilis is frequently used in detection of water ammonia-nitrogen pollution produced by industrial pollutant discharge as well as agricultural and domestic sewage discharge due to its rapid propagation and easiness of culture in vitro. This study was conducted to assess the effect of ammonia-nitrogen pollution on growth, development and propagation of individual and population of Brachionus plicatilis. Brachionus plicatilis was received the treatment with different concentration of non-ionic ammonia, and the intracellular activity of superoxide dismutase （SOD） and glutathione S-transferase （GST） was determined at the different time-points of treatment. The results showed that low concentration of non-ionic ammonia had no obvious effect on longevity of Brachionus plicatilis; when the concentration of non-ionic ammonia in seawater reached up to 0.01‰ ,the longevity and total fertility of Brachionus plicatilis was significantly reduced; the decrease of the total fertility was probably associated with the presence of death in the growth period. The population experiment results showed that the maximum environmental carrying capacity of the Brachionus plicatilis treated with high concentration of non-ionic ammonia was reduced, and the male Brachionus plicatilis appeared earlier. The high concentration of non-ionic ammonia reduced the activity of the two anti-oxygen protective enzymes of SOD and GST; the increase of free radicals and the decrease of anti-oxygen activity accelerate the aging of Brachionus plicatilis, which was speculatively considered as one of the reasons associated with the longevity shortening of Brachionus plicatilis individual. The results obtained in this study reveal the inhibitory effect of high concentration of non-ionic ammonia on growth and propagation of Brachionus plicatilis at both individual and population level. Furthermore, the underling mechanisms were assessed at the cellular level, which provides favorable evidence for confirming the adverse effects of non-ionic ammonia pollution on marine plankton.