The invention discloses soft hydrolysis-resistant low-crystallinity-degree polyether type wet process polyurethane resin for sofa leather and a preparation method of the resin. The wet process polyurethane resin for the sofa leather is mainly prepared from diisocyanate, polyhydric alcohol compounds, micromolecular dihydric alcohol chain extender, micromolecular diamine chain extender, a catalyst, antioxygen, a solvent and reaction terminating agent methyl alcohol. The polyhydric alcohol compounds include polypropylene oxide dihydric alcohol and polyester diol. The mass ratio of polypropylene oxide dihydric alcohol to polyester diol is 1-2:1. An excessive pre-polymerization method process is adopted in the polyurethane synthesis process, the micromolecular amine chain extender is embedded into polypropylene oxide diol, the rigidity and cohesion of polypropylene oxide diol can be obviously improved, and meanwhile, by the adoption of high-rigidity polyester diol, the condensation speed of the resin and the hole pattern supporting intensity after the leather is formed are guaranteed. Thus, after the prepared hydrolysis-resistant resin forms the leather, the advantages of being full in hand feeling and excellent in rebound resilience are achieved.