In order to study the soil mechanical properties of soft soil composite foundation of Xiachongkou Gate sluice treated by loose artificial sealed piles，laboratory tests were carried out to study the effects of height diameter ratio and compactness of loose materials on soil mechanical indexes. The test shows that the smaller the height diameter ratio of the specimen is，the higher the bearing strength will be and more significant the brittle deformation will be；With the gradient change of height diameter ratio，there is an average decrease of 10.3% and 14.8% respectively under the confining pressure of 100kPa and 400kPa. The greater the compactness of granular filler is，the higher the strength of composite soil and the more significant effect of confining pressure with a relatively long strain hardening section will be. The shear characteristic parameters are negatively related to the height diameter ratio，and positively related to the compactness of bulk materials. The former affects the cohesion，while the latter mainly affects the internal friction angle.The research results can provide reference for the design and application of artificial piles in soft soil and other unfavorable soil layers.