Objective   To explore the cause that chlorodisinfectant unable to control proliferation and propagationg of legionella pneu mophila f or a long time. It is to provide guide for seeking the way that can control proliferation and propagationg of legionella pneumophila in air-conditioning cooling water for a long time.

  Methods   By periodically detecting increase or reduce of legionella pneumophila and concent ration of total organic carbon(TOC), No₃^--N, total bacterial member and alga in 7 air-conditioning cooling water and constituting ecopatterns of legionella pneumophila as well as tesing legionella pneu mophila in air at the same time, proliferation and propagationg of legionella pneu mophila were investigated in air-conditioning cooling water.

  Results   The appear or disappear and raise or down of legionella pneumophila member has mainly relation to water temperature, total organic carbon(TOC), No₃^--N, and alga member(Raphidiopsis, Pediastrum and Freubaria). In the best ecoenvironment coped from air-conditioning cooling water, proliferative speed of legionella pneumophila can attain to a fold as an hour and keep the multiplicative proliferation in this experimentally 3 days. When legionella pneu mophila member in the water attained to 4.2×10⁴/ml, legionella pneumophila was tested in the air 30 centimetre above the water. When legionella pneumophila just was given, its proliferative speed also attained to a fold as an hour in the ecoenvironment of alga member reduce but proliferative speed was more and more down. After 3 days legionella pneumophila member in the ecoenvironment of alga member reduce only was 1/160 as that member in the ecoenvironment of alga member increase.

  Conclusion   Legionella pneumophila in the air-conditioning cooling water below 20℃ was rather liveless than rest. The proliferative speed of legionella pneumophila was significanly related with alga member, total organic carbon (TOC)and No₃^--N besides temperature. It might be a fundamentally controlling legionnaires'disease outbreak method to destroy legionella pneumophila ecoenvironment and reduced its proliferative speed to cut off its propagationg among cooling towers by a certain rate removing alga, total organic carbon(TOC)and No₃^--N in air-conditioning cooling water.