Because of the artificial backfilling, the geological and hydrological conditions are complicated in Dalian near sea region, which was alluvial marine sedimentation terrace. The natural deposit soil and rock exists with strong permeable backfilled miscellaneous soil-filling. Pile foundation pit enclosure structure, water-proof curtain and deep well point dewatering were adopted for ultra large deep foundation pit excavation. By 2 pile tests and process parameters optimization, it was proved high pressure jet grouting pile waterproof curtain achieved ideal effect.