Abstract： In order to study the bearing behavior of composite foundation with flexible pile at longterm load, comparative experiments of composite foundation with rammed soilcement pile with or without lateral restraint at longterm load were conducted. Settlement marks were laid on the surface of composite foundation to measure the sedimentation of pile and soil, from which the variation law of the sedimentation of pile and soil with time could be obtained. By laying earth pressure cells on the surface and bottom of the foundation and building PVC tube with stain gauge in pile shaft to measure the stress value, the stress variation of pile top and soil top, the stress ratio of pile soil and pile shaft tress change with time were analyzed.  The results of comparative tests show that at longterm load, the performance of composite foundation of rammed soil-cement pile with lateral constraint length piles is obviously better than that without lateral restraint, which can greatly shorten the time step in stable phase (approximately 64%) and reduce the settlement after construction (approximately 29% to 42%), and decrease the pilesoil stress ratio approximately 39%, hence adjust the distribution of axial force of pile shaft significantly. It can be acknowledged that when soft soil is treated with flexible pile, the settlement after construction can be effectively reduced and bearing capacity of subgrade can be improved if rigid long pile is set as lateral restraint.