The present invention relates to an anode active material for a lithium secondary battery, comprising a carbon material, and a coating layer formed on the surface of particles of the carbon material and having a plurality of Sn-based domains having an average diameter of 1 μm or less. The inventive anode active material having a Sn-based domains coating layer on the surface of a carbon material can surprisingly prevent stress due to volume expansion which generates by an alloy of Sn and lithium. Also, the inventive method for preparing an anode active material can easily control the thickness of the coating layer.