Increased floors on an office building in Hunan petrochemical Company caused uneven subsidence,resulting in a large amount of fissures on the building and putting it at the risk of demolition. Therefore it was decided to consolidate the building. Detailed research into the causes for uneven subsidence and comparison of schemes decided that hign pressure jet grouting method would be adopted for consolidation. Mechanical calculation on the consolidation engineering , check of rationality and correctness of design parameters, construction method and technology of jet grouting pile in sand layer are introduced. Observation and mechanical check calculation after completion of consolidation shown that high pressure jet grouting method is highly effective for foundation consolidation.