Influence of separate-layers’ thicknesses and interfaces in layer [Pt/Fe]n film compositions with thickness of 30 nm (n = 1, 2, 4, 8) deposited by magnetron sputtering on SiO$_{2}$(100nm)/Si(001) substrate on the formation of their structure and phase composition at annealing in a vacuum in the temperature range of 400—900°C is investigated. As shown, the increase in amount of interfaces at reducing layer thickness promotes in activation of diffusion processes on the interfaces and the formation of disordered $A1$-FePt phase in [Pt(4.2 nm)/Fe(3.2 nm)]$_{4}$ composition and partly ordered regions with tetragonal distortions in [Pt(2.1 nm)/Fe(1.6 nm)]$_{8}$ composition already at deposition. The $A1$-FePt $\rightarrow$ $L1_{0}$-FePt phase transformation in film compositions take place during annealing at 700°C. The greater amount of grains oriented in [001] direction perpendicular to substrate is formed in [Pt(4.2 nm)/Fe(3.2 nm)]$_{4}$ film compositions. The less degree of ordering is typical for [Pt(2.1 nm)/Fe(1.6nm)]$_{8}$ film composition. Additional amount of interfaces restrains grain growth of ordered $L1_{0}$-FePt phase at heat treatment in temperature range of 700—800°C.