The work is aimed to theoretical investigation of orbital and magnetic structure of manganites. The orbitally-dependent exchange interaction model was used in order to describe the superexchange interaction in all range of RMnO3 (R=La, Pr, Nd, Tb, Dy, Ho) orfhorhombic compounds. The model of nearest-neighbour and next-nearest neighbour exchange was used to describe the magnetic structures of manganites with small rare-earth ion sublattice (R=Dy, Tb, Ho). We investigate different types -A, E, non-collinear - of magnetic structures. The models of NMR spectra calculation of Mn3+ ion in RMnO3 compounds are proposed. The theoretical study of the magnetic structure could distinguish The NMR-spectra of antiferromagnetic (A or E) or strongly non-collinear ordering type.