The present invention discloses a cavity preparation assembly and a guiding sleeve for immediate implantation in an oral molar region, wherein the guiding sleeve comprises a lower sleeve and an upper sleeve disposed on a top of the lower sleeve, center portions of the upper sleeve and the lower sleeve each has a guiding hole and the guiding holes of the upper sleeve and the lower sleeve are connected, and an axis direction of the guiding hole is a vertical direction; sidewalls of the upper sleeve and the lower sleeve are each provided with a slit passing through the sidewalls, and the slit of the upper sleeve and the slit of the lower sleeve are located on a same side of the cavity preparation guiding sleeve; the upper sleeve is further provided with an installation plate on both sides of the slit, the installation plate is connected to the sidewalls on both sides of the slit of the upper sleeve. The cavity preparation assembly comprises a depth calibration drilling tool and a plurality of guiding sleeves. The present invention not only facilitates observation of the position of the drilling tool, prevent the drilling tool from sliding, but also provides the cooling water channels to cool the drilling tool, avoiding osteonecrosis. The depth calibration drilling tool performs precise cavity preparation according to the preparation depth.