Aiming at special structure of T-shaped bidirectional soil - cement deep mixing pile , drill and extract core samples in the test pile , then put the plastic pipe which affixed with strain gauges into the drill holes, based on static load test , the paper calculated the pile axial force of pile body and additional stress, and then analyzed the bearing features related to the expanding head height. Results show that the axial force of pile body and the additional stress are mainly distributed in the range of expanding head height, and there are a greater axial force difference and the phenomenon of stress concentration at the variable cross section of pile. It ultimately concluded that the most suitable height of enlarging head in deep soft soil is 4 -5 meters and the minimum height should not be less than 2 meters.