In the formation of sea reclamation region, backfill only experienced short time with most filling material of excavated-stone, so the loose structure, large interstice, smooth connectivity of underground water & sea water and strong scouring by tidal action existed, which brought difficulties in borehole completion and slurry solidification for water-proof curtain construction. Based on the detailed analysis on the engineering geological condition, practice and innovation were carried on for hole boring technology and construction sequence of jet-grouting pile. Good construction effect was achieved with reasonable improvement and optimization.