The sludge landfill, located in the north of Shenzhen airport, is in rang of the airport expansion field. The solidified sludge at landfill will be used as the foundation. Geotechnical properties of the solidified sludge were investigated, including organic content, water content, initial void ratio, limit content, particle-size distribution, microstructure compression consolidation properties and shear strength. The results showed that the organic content of solidified sludge decreased with the increase of depth, related to the degree of degradation. The change rules of water content and initial void ratio were the same as the organic content. The change of organic content after landfilled was the internal reason for the changes of water content and initial void ratio. The solidified sludge had high limit content, and though the values of liquidity index are greater than 1, the apparent state of sludge performances solid state. Solidified sludge was porous medium and its structural was poor. Solidified sludge was high compressive and under consolidated soil. The consolidation coefficients of solidified sludge were close to conventional muddy soil and showed a decreasing trend with the increase of consolidation pressure, presenting a typical large deformation consolidation properties. With the increase of depth, the shear strengths of the undisturbed solidified sludge increased from 13.8kPa to 23.7kPa, and the shear strengths of remoulded solidified sludge increased from 13.0kPa to 14.3kPa. The intensity of sludge structure played a decisive role in the changes of shear strength.