For 100 meter depth geological drilling in offshore sand, directly coring in non-cementing loose sandy sediments formation without casing greatly reduces labor intensity and improves working efficiency. Hole wall collapsing, difficult cuttings upward, sand gushing and drill pipe sticking are often encountered in the core drilling investigation in offshore sand of Yellow Sea. The paper summed up the drilling process technology for the well of 100 meter depth in offshore sand and the prevention measures for downhole accident.