The utility model relates to an oil drilling technical field that cores, in particular to reduce two -way injection core bit of chip hold down effect. The urceolus is connected to the device's core bit body upper end, wall connection inner tube and sealed through the sealing washer in the core bit body, and the annular space is linked together with inside lower the injections hydrophthalmia of core bit body between urceolus and the inner tube, and lower injection water holds the export to set up in core bit body bottom now, and the inside drilling fluid that is equipped with of every wing goesupward the runner, and the drilling fluid goes upward the runner import and sprays the hydrophthalmia down and feeds through, and upper nozzle is installed in drilling fluid upstream way exit. The utility model discloses a can reduce the influence of chip hold down effect effectively, improve the drilling speed of coring, shorten the engineering time of coring, reduce the rock core erosion, improve the rock core yield, guarantee the rock carrying ability of drilling fluid in the annular space simultaneously, prevent that detritus and the wall of a well from falling the piece and piling up oncore bit upper portion, the possibility of reduction occurence of failure.