A device suitable for atomization and injection of a hydrocarbon batch into a reaction chamber comprises an admission and mixing chamber (5) for the liquid hydrocarbon batch introduced into the device by a tube (8) and for an atomization gas introduced into the device by a cylindrical casing (9) containing tube (8). Casing (9) is extended by a Venturi tube (6) which has a convergent part connected upstream to cylindrical casing (9) and a divergent part connected downstream to a hemispheric tip (7) that leads, by a rectangular slit with an opening angle (16) between about 100 and 115 degrees, to the reaction chamber. The device can be used in processes for catalytic cracking of heavy hydrocarbons.