A geosynthetic-reinforced pile-supported (GRPS) embankment is a complex soil-structure system. The response of a GRPS system is affected by the interactions among its five linked elements, namely the geosynthetic (a synthetic product used in civil engineering to stabilise the terrain), foundation, granular platform, fill soil, and geological media underlying and surrounding the foundation. The key load transfer mechanism in a GPRS embankment is a combination of various phenomena that include arching in the fill layers, tensioned membrane effect of the geosynthetic, frictional interaction, and support of the soft subsoil. Referring to the current numerical and experimental studies, a new theory has been developed in this study by combining the arching theory for the soil layer and the tensioned membrane theory for the geosynthetic. The subsoil effect with both linear and non-linear models and the frictional interaction are also included in the proposed method, thereby providing a more comprehensive design approach than the earlier methods that considered only either the tensioned membrane theory or the arching theory. It is demonstrated in this work that the proposed method produces results that are in good agreement with the experimental observations.