The polyurethane (PU)/hydrophobic silica gel (HSG) fibrous membranes with the hydrophobic and breathable surface was fabricated via electrospinning. By employing the HSG incorporation, mechanical properties, thermal stability, and waterproofness of the composite membranes could be improved. The porous structure of the membranes would be regulated by tuning the temperatures of thermal treatment. When HSG content increased to 3 wt%, the PU/HSG composite membranes possessed remarkable tensile strength of 6.3 MPa and high water contact angle (WCA) of 134 degrees. Furthermore, the maximum WCA (142 degrees +/- 1 degrees), good hydrostatic pressure (5.45 kPa), large water vapor transmission rate (8.05 kg/m(2)/day), and high air permeability (9.25 L/m(2)/s) of the composite membranes could be achieved by heat treatment at 120 degrees C. The resultant membranes performed significantly better when compared to the pure PU membranes under the same conditions, such as the higher tensile strength (100%), better waterproofness (200%), and stronger breathablity (25%). POLYM. ENG. SCI., 58:1381-1390, 2018. (c) 2017 Society of Plastics Engineers