Phase structure of mixture of poly(4-vinylphenol) (PVPh) with N,N-dimethyl-octadecylamine (NDOA) is investigated. It is shown the PVPh-NDOA mixtures form ordered phase in solid state. The ordered structure in the mixtures is formed by 1:1 stoichiometric aggregate of NDOA and repeating unit of PVPh. Further, it is shown that short period of the structure of the mixture is almost invariant from that of NDOA crystal and long period of the structure of PVPh-NDOA aggregate is larger than that of NDOA crystal. Hence, it is predicted PVPh chain lies vertical to alkyl chain of NDOA in the ordered phase.