In view of abnormal high pressure， the narrow three-pressure window and faults in the high-pressure zone in Well L in Bohai Oilfield， fine pressure-control drilling technology was developed through use of fine pressure control surface equipment and proper control of drilling parameters to reduce the risk of both leakage and blowout in the same layer during well drilling， and achieved early prevention， early discovery and early settlement of overflow. In combination with safe operation measures such as pressure-controlled drilling， connecting drill pipe stands， and tripping of drilling strings， Well L was successfully side-tracked， laying a technical foundation for the exploration and development of the abnormal high-pressure area in Bohai Oilfield.