Abstract: Waterproof and moisture-permeable functional membranes are widely used in the fields of outdoor textiles and medical protection. However, traditional fluorine-containing microporous membranes pose environmental risks. Therefore, the development of fluorine-free and environmentally friendly fiber membranes is an important direction for functional membranes. In this paper, polysulfone (PSU)/lithium chloride (LiCl) nanofibrous membranes were first prepared by electrospinning technology, and then hydrophobically modified with amino-functionalized polysiloxane (AMP). As the LiCl concentration increased from 0wt% to 0.01wt%, the conductivity of the spinning solution increased, the fiber diameter decreased from 769.1 nm to 570.4 nm, and the hydrostatic pressure also increased from 4.2 kPa to 16.1 kPa. When the LiCl concentration was 0.01wt%, the strength of the fibrous membrane was 2.7 MPa, the elongation at break was 46.4%, and the moisture permeability was 1899.6 g·m⁻²·d⁻¹. Therefore, the PSU/LiCl-0.01 composite fibrous membrane was selected for subsequent hydrophobic modification. The fluorine-free hydrophobic modification of AMP significantly improved the waterproofness of the fibrous membrane, and the hydrostatic pressure of the fibrous membrane increased from 16.1 kPa to 50.5 kPa. The adhesion structure provided after AMP modification could effectively improve its mechanical properties, and the strength increased to 4.8 MPa, nearly 1.8 times higher than that of the untreated PSU/LiCl-0.01 membrane. In addition, although the moisture permeability decreased to 1187.3 g·m⁻²·d⁻¹ after AMP hydrophobic modification, the demonstration experiment showed that the fibrous membrane still had good liquid-repellent and air-permeable properties. The above research results indicate that the prepared fluorine-free and environmentally friendly PSU/LiCl@AMP nanofibrous membrane shows application potential in fields such as outdoor sports and medical protection.