The annual change of water level process in the Lake Poyang was summarized on the characteristics and types of annual and inter-annual water level variation in the past 5 years from the measured hydrological data. Based on these, the inter-annual change processes of water transparency, temperature and depth gradient were also studied. Combined with the investigation results of biological resources and their dynamic changes from “the scientific survey of Lake Poyang”, focusing on the three typical years of 2009, 2010 and 2011, the correlation between the process of hydrological element variation and the biological reproduction, growth, maturity or death in Lake Poyang wetland was explored: submerged plants were flooded 1.5-2.0 m under the water with transparency less than 20-30 cm and most of them died while swelling between April and June; low water level from March to June and June to September resulted in the spawning and feeding grounds of settled fishes narrowed; too high or too low water level from October to December impacted winter migratory birds to move into or perch in the Lake Poyang wetland. The study had preliminarily presented the control effects of hydrological rhythm on growth and survival of organisms in the Lake Poyang wetland and reflected the eco-hydrological process of Lake Poyang in a certain sense.