The present invention relates to a process for straightening keratin fibers, preferably hair, comprising the steps of: (i) applying onto the keratin fibers a composition for straightening keratin fibers； (ii) wrapping the keratin fibers, onto which the composition is applied, with at least one wrapping means in order to keep the keratin fibers wet； (iii) straightening the wet keratin fibers with a heating iron at a temperature of more than 100 °C, preferably more than 100 °C and less than 210 °C, and more preferably from 110 °C to 200 °C； (iv) unwrapping the keratin fibers； and (v) optionally rinsing and/or drying the keratin fibers, wherein the composition for straightening keratin fibers comprises (a) at least one compound chosen from alkylaminosulfonic acids and those represented by specific chemical formulae, and the composition for straightening keratin fibers has a pH of from 7.5 to 12.0, preferably from 8.0 to 11.5, and more preferably from 8.5 to 11.0. The present invention can provide keratin fibers with sufficient straightening effects which can last a long time, as well as conditioning effects (e.g., providing the keratin fibers with softness and smoothness), with less damage than conventional straightening processes, and good usability (e.g., short processing time without drying before heating).La présente invention concerne un procédé de lissage de fibres de kératine, préférablement du cheveu, comprenant les étapes suivantes : (i) application sur les fibres de kératine d'une composition de lissage de fibres de kératine； (ii) enveloppement des fibres de kératine, sur lesquelles la composition est appliquée, avec au moins un moyen d'enveloppement afin de maintenir les fibres de kératine humides； (iii) lissage des fibres de kératine humides avec un fer à lisser à une température de plus de 100 °C, préférablement plus de 100 °C et de moins de 210 °C, et plus préférablement de 110 °C à 200 °C； (iv) désenveloppement des fibres de kératine； et (v) éventuelleme
