Abstract: Objective To study the variational rules of biological stabilization.Methods Detection was made on the parameters such as heterotrophic plate counts(HPC)assimilable organic carbon(AOC)and biodegradable organic carbon(BDOC)in a northern city distribution network of China.Results Temperature was the most important factor that infected the result of HPC,ithad evidently positive correlation with HPC.AOC content seemed to have weak correlation with free chlorine,and had no correlation with amount of heterotrophic bacteria.BDOC had some negative correlation with free chlorine,and had some positive correlation with amount of heterotrophic.Conclusion The control of AOC,disinfectant residue and turbidity should be combined to be considered in order to control the bacteria regrowth in distribution network.The relationship among bacteria,AOC,BDOC,disinfectant and the hydraulic factor in the distribution network is quite complex,and it's far different from one network to another.The physical and chemical reactions in the network still need further research.