Abstract: The problem of oozing slurry is salient and difficult to solve in the large crossing drilling engineering.The main reason of oozing slurry is improper drilling fluid,the drilling cuttings can be not discharged from bore hole.It results in annulus overpressure and breaking down overlying stratum,and then oozing slurry in the ground.During indoor or outdoor experiments,we founded the mud system of preventing oozing slurry with main performances of dilution shearing(flow resistance reducing),filtration control,against sloughing and so on.Field application proves that the mud system can reduce annular mud pressure effectively,and solves the problem of oozing slurry radically.