Abstract: Composite foundation with rigid-flexible piles is a new type of ground treatment.There are disputes on this kind of foundation with or without cushion because pile-soil interaction mechanism of this foundation is not known clearly.Static load tests of this foundation were carried out under different situations in Wenzhou.Earth pressure cells,strain meters and stress meters were embedded beneath the bearing plates at different positions.Sensors were monitored in the process of static load test.It was shown that load-settlement,distribution of soil reaction,pile shaft stress distribution,load transfer mechanism of rigid-flexible piles composite foundation with cushion were different from those without cushion.Since the performance of the former was better than that of the latter,composite foundation with cushion was recommended to be applied.