FT-30, a typical, aromatic polyamide membrane, is formed by interfacial polycondensation (IP) reaction between m-phenylenediainine (MPD) and benzene 1,3,5-tricarboxylic acid, chloride (TMC) monomers. To investigate its microscopic characteristics, We performed atomistic molecular simulation using the hybrid MC/MD reaction method modified to allow intercellular chemical bonds stretching over the periodic boundaries. Starting with appropriate monomer model systems, we succeeded, in making Membrane models by simulating, a succession of condensation reactions. Through an analysis comparing our calculation, results for the degrees of polymer cross-linking (DPC) and the composition ratios to the experimental results, we clarified the MPD/TMC mixing ratios in the near-surface active (NSA) and interior active (IA) regions associated with the reaction mechanism of IF. Further, we executed water diffusion simulations using the mernbrane model of the IA region Values of-the total mass density of the hydrated membrane and the partition coefficient K to be in good agreement with the experimental Ones. In conclusion, the present computationally modeled polyamide membrane has sufficient fidelity to the actual membrane and should be considered a stable spatial structure in the local equilibrium state under a nonequilibriurn stationary state of permeation.