A method for synthesising hexagonal GaN on a Si(113) substrate with a nanostructure of about 75 nm on its surface (NP-Si(113) substrate) is proposed. It has been established that the method of the metal-organic chemical vapor deposition on such a substrate makes it possible to form a semi-polar layer of GaN(11-22) with half-widths of the X-ray diffraction curve ωθ ~ 30 arcmin. It is shown that during epitaxy from organometallic compounds in hydrogen atmosphere at the initial stages of growth the layer orientation is given by the direction of Si(111) plane of nanocanals in NP-Si(113) and the growth rate of GaN layer in (11-22) and (0001) planes direction is comparable.