The invention relates to an environment-friendly water-soluble polyurethane textile softening agent preparation method. The invention is characterized in that the method is that a pre-polymer with theterminal group of-NCO is generated with the diisocyanate and a diol compound first, then the dimethylol propionic acid and a chain-extension agent are used for a chain-extension reaction, and finallythe pH value is adjusted by triethylamine to the neutral level and deion water is added and stirred, so the environmental-friendly watery polyurethane textile softening agent is got. The softening agent is applicable in the textitle after-finishing to promote the softness performance and the pendency performance of the textile and provides the textile with the feeling of firmness. The invention is also characterized in that no harmful solvent is volatilized during the course of solidification. Thus, the invention is completely consistent with the environmental protection requirement of an auxiliary chemical agent.