Dynamics in Benzo[a] pyrene (B[a] P) concentrat ions in soil as influenced by ryegrass plants (Lolium multiflorum Lam) were studied in a greenhouse experiment.During the 120 days of plant growth, the extractable B[a] P concentrations in the soils decreased with time and were much less in soil grown with ryegrass plants.In the planted soil with application rate of B[a] P 1, 10, 100 mg kg^-1 soil, B[a] P biodegradability amounted to 82.3%, 74.0% and 55.9%, respectively.The planted soil had higher activity of polyphenoloxidase as compared with the unplanted soil.B[a] P concentrations in the plants ranged from 0.06 to 3.60 mg kg^-1 and declined with the increasing number of days of plant growth.Ryegrass enhanced rhizo-degradation of B[a] P in the contaminated soil.Increase in ryegrass growth and polyphenoloxidase activity in the rhizosphere soil can improve the bioremediation capability of of B[a] P-contaminated soil by ryegrass plants.