Heteroepitaxial growth of fluorinated long chain molecules (n-C20F42) on two different substrates was evaluated by an energy dispersive grazing incidence xray diffractometer. It was found that the n-C20F42 molecules grow normally and epitaxially on the CaF2(111), aligning their [100(hex)] in the CaF2[110] with the inclination of about 12 degrees, through slight interactions between the terminal CF3 and CaF2 surface. While, the molecules evaporated on the Au coated KCl(001) was revealed to form polycrystalline structures in in-plane direction, due to the surface roughness and difference in the grain sizes between n-C20F42 and Au films.