Abstract : From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technic of Bloch oscillations, which allows us to transfer a large number of recoils to the atoms. A velocity sensor, based on velocity selective Raman transition, allows us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 ppb, in conjunction with a careful study of systematic effects (5 ppb), lead us to a determination of alpha with an uncertainty of 6.7 ppb. This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry.