Abstract: The load-deformation behavior of pile-supported geosynthetic reinforcements (GRs) is a complicated three-dimensional mechanical problem, and so far the 3-D analytical methods have not been well-established. Therefore the GRs with piles in square-type layout under 3-D conditions are taken as the research objects, which are regarded as the spacial membranes under the combined effect of the upper load and the subsoil reaction among piles. The partial differential equilibrium equations are derived based on the minimum potential energy principle. For the conditions of uniform load and without subsoil reaction, the analog equation method in the membrane analysis is used to solve the equations in view of their complex forms and highly nonlinear characteristics. Then the deformation and tensile force of GRs are accordingly calculated, and the 3-D analytical method for the pile-supported GRs is established. Finally, the rationality of the method is validated primitively by comparing the calculated and observed results of a field test example.