Aiming at the adverse effects of wall concrete spalling, effective cross section reduction and water quality deterioration due to the phenomenon of biological fouling occurring frequently in Chinese water diversion projects, based on water diversion project in the middle route of the South-to-North Water Diversion Project, laboratory model experiments were carried out under different area ratios, and porous media domain was used to simulate the three-dimensional flow field of a pressurized pipeline under biological attachment dominated by limnoperna fortune.The influence of limnoperna fortunei attachment on the flow capacity of the pressurized pipeline was analyzed.The results show that the flow in the pressurized pipe presents the main flow deviation, and the particle momentum exchange near the wall is more intense.Section roughness was positively correlated with the attachment thickness and the area ratio.At low density, the main influencing factor was the attachment number of limnoperna fortunei.At high density, adhesion thickness is the main factor.