Abstract: The growth of heterotrophic (HPC) in water distribution pipes was studied, simulation pipeline reactors were used to simulate the water situation. Water samples were prepared in a laboratory to simulate Class Ⅱ, Ⅲ andⅤ or worse of the surface water standard.Resultsshow that the quantities of HPC in the biofilm are significantly higher than those in the bulk water, and are stabled at 1. 1 × 105, 2.8 × 10⁵, and 5.9 ×10⁵CFU/cm², respectively, after 45 days. UV₂₅₄ concentration and orthophosphate (PO₄^3-) concentration and turbidity in raw water are all positively correlated with the quantity of HPC in the biofilm, and the correlated coefficient are r = 0. 506, 0. 552, and 0. 272, respectively.