Analyzing　the　cooperation　mechanism　of　piles,　soil　and　cushion,　the　method　to　calculate　the　stress　ratio　of　piles　to　soil　is　introduced　by　considering　harmony　working　of　piles,　soil　and　cushion　in　composite　foundation.　The　factors　influencing　the　stress　ratio　of　piles　to　soil,　such　as　cushion　modulus,　soil　modulus　of　piles　end,　rigid　ratio　of　pile　and　soil,　pile　length,　area　displacement　ratio,　are　discussed　by　calculating　stress　ratio,　and　the　bearing　behavior　of　rigid　pile　composite　foundation　are　analyzed.