The artificially filled coral islands and reefs have a special stratigraphic structure， mainly of coral sand and coral debris， which makes it difficult to core and form holes. Taking the geological drilling and coring project on an island and reef in the South China Sea as an example， a series of corresponding technical measures were adopted according to the lithological characteristics of the formation： casing while drilling and dry core drilling for the upper loose or weakly cemented sand and gravel； a sand-bailing tool designed for complete circulation loss formation to ensure a clean borehole in reef limestone； drill bits with advance side nozzles for the soft and hard alternate beds； small-diameter dry core drilling for the silt-sand layer. The technology has achieved good results in drilling of 18 boreholes， which can provide a reference for subsequent coring in coral reef formations.