Abstract: A wake area where electrons and ions currents are diferent wil form behind a spacecraft in LEO cold,dense plasma environment.The wake effects will devlelop a different charging on the surface of a spacecraft.In this paper we analyse the physical mechanism of wake charging effects.A two-dimensions simple calculation model.is discussed.Then a computer code on particle-in-cell method are developed.The spacecraft wakes potential of diferent scales are caculated,including high electrons entering.The results prove that wake effects are dependent on the scale of a spacecraft and the energy.of electrons in wakes.