The egg ratio of Brachionus diversicornis during summer and autumn in Lake Jinghu, Wuhu City, Anhui Province, was investigated, and the relationships between the egg ratio and its population density, food resource, potential predators and competitors, water temperature, transparency, dissolved oxygen, pH value as well as the N-NH+4 concentration in water column were also analyzed. The results showed that in the big region of the lake, the egg ratio of B. diversicornis ranged from 0.095 to 1.073, with an average of 0.293, and was negatively correlated with both the rotifer population density and water transparency (r was -0.346 and -0.329, respectively), but positively correlated with both the total Chl-a content and the Chl-a content in water filtered through 25 μm net (r was 0.457 and 0.417, respectively). An obvious time-lag effect of Trichocerca density on the egg ratio of B. diversicornis was observed. Asplanchna density was a main factor affecting the egg ratio of B. diversicornis during the end of June and the beginning of September (R2=05074). In the small region of the lake, the egg ratio of B. diversicornis ranged from 0.0471 to 0.5455, with an average of 0.194, and was positively correlated with only the total Chl-a content (r = 0.356). All the results stated above indicated that the factors affecting the egg ratio of B. diversicornis have spatial and temporal heterogeneity.