To investigate the effects of macropore flow in farmland soil and colloid release caused by agricultural activities on the vertical migration of phosphorus and groundwater pollution,parallel soil column experiments were conducted using agricultural soil from the Taihu Lake Basin. The results show that the release of colloid (with a concentration of about 50 mg/ L) in soil accelerated the vertical migration of colloid and available phosphorus,and the leaching rate of available phosphorus at the soil column bottom (100cm in depth) reached 0.15kg/ (m²·d),about 15. 4% higher than it was with no obvious release of soil colloid. Furthermore,the existence of macropores (5% in volume) in soil significantly increased the leaching rate of available phosphorus,with a value of 29. 9 kg/ (m2·d) at the soil column bottom. The preferential flow caused by macropores played a critical role in the leaching of colloid and available phosphorus. However,the release of soil colloid accounted for 3. 2% of the increase of the leaching rate of available phosphorus when macropores existed. Soil colloid release altered the chemical characteristics of soil,such as pH and electric conductivity,and then influenced the transport of solutes in soil. Preferential flow caused by macropores and soil colloid release caused by agricultural activities exist across the agricultural area of the Taihu Lake Basin. Macropores and soil colloid accelerated the vertical infiltration of phosphorus,which increased the risk of groundwater pollution caused by phosphorus.