Seasonal variation of bacterioplankton growth rate was measured with 3H- thymidine tracing method in Gehu Lake, along with the measurement of sedimentation of detritus, content of organic matter and C/N ratio of particulate and sedimented matter. The results show that there exist marked seasonal variations in growth rate of bacteria on season,sedimented matter, and is highly related to water temperature, organic matter concentration, C/N ratio and sedimentation of organic matter. The bacteria growth rate is an important parameter of structure and function of lake ecosystem, and also constitute the base for fisheries exploitation.