It is an important part of the construction of the “Belt and Road” seismic monitoring network to carry out reaming and upgrading of CSDP-2 hole of the “Deep Marine Seismic Monitoring Network”. By summarizing the drilling process used for reaming CSDP-2 hole in the South Yellow Sea， a set of drilling technology suitable for offshore deep drilling has been developed： including rotary water well drilling rig which was used on the drilling platform to make the equipment modular and portable； Mud pulse MWD which can effectively save survey time and improve drilling quality from the single point inclinometer. Seawater based low solid polymer drilling fluid which has effectively tackled the problems such as mudstone expansion and mud production in water sensitive formation， circulation loss in broken formation， hazard gas emission from gas bearing formation so as to prevent downhole incidents. The research results can provide technical support and reference for subsequent deep ocean drilling.