Abstract : The main theme of this thesis is the measurement of the inclusive electron cross-section from the decays of heavy flavour quarks (b and c) with the ATLAS detector in proton-proton collisions at sqrt(s)= 7 TeV at LHC. The calibration of the electromagnetic calorimeter and the electron reconstruction play a central role for the analysis presented in this thesis. These topics are discussed in the first part of the manuscript. The study of the systematic uncertainties affecting th e cells' reconstructed energy due to the variation of the electronic calibration constants f the readout chain of the calorimeter is presented. Then, the procedure developed for the ATLAS detector to reconstruct the physics events is described. Cases of misidentif ied particles are discussed and a study estimating the rate of fake leptons in multi-jet events is presented. The second part of this thesis is dedicated to the inclusive electron cross-section from the decay of heavy flavour quarks. An overview of the theoretical predictions is given as an introduction to the experimental measurement. The measurement has been performed with a data sample corresponding to an integrated luminosity of 1.3 pb-1 and recorded during the startup of ATLAS. Besides its theoretical interest, this measurement also allows to verify the detector performances directly from data. The background subtraction and the electron identification efficiency are estimated using data driven methods.