In order to ensure the safe and smooth drilling of Well Longtan X3, the first directional well to be drilled in bed rock, a lot of calculation has been done in the drilling engineering design with the Landmark software on the well structures, BHA, bit optimization, drilling fluid optimization and borehole cleaning to cope with the tricky issues such as circulation loss, well deviation and wellbore instability, poor drillability of hard rocks, difficult borehole cleaning; at the same time, statistical analysis and screening were made for optimizing of the engineering design. As a result, drilling operations have been carried out successfully without any accidents, indicating that the engineering design was proper, and the technical difficulties in drilling operations can be overcome.