Top Physics with the ATLAS detector at LHC

In 2009, the Large Hadron Collider (LHC) will provide first proton-proton collisions. The LHC will be the first top quark factory. After the Top quark discovery and first measurements at Tevatron, the LHC will open a new opportunity for precision measurements of the Top quark properties. Some of the early LHC physics results could come from Top physics, leading to a major improvement of Top quark understanding and eventually opening a window for physics beyond the standard model. Studies performed at 14 TeV in order to estimate the potential of ATLAS to perform an accurate determination of the top quark pair and Single Top production cross section, to measure the top quark mass, the top quark charge, the W and Top polarisations, the Standard Model decay (t-> bW), to search for rare top quark decays and ttbar resonance production are reviewed in this talk