Electrospun nanofibrous membranes with outstanding mechanical property, breathability, and waterproofness are critical in protective fields; however, great challenges still remain in creating such functional materials. A novel polyvinylidene fluoride (PVdF)/polyvinyl butyral (PVB) breathable-waterproof membrane with robust mechanical performance is fabricated by introducing thermal post-treatment into electrospun membranes. Embedding of PVB enriches the pristine PVdF nanofibrous membranes with bonded network, optimized pore size, and porosity. The composite membranes are endowed with robust tensile stress of 10.5 MPa and good breaking elongation of 64.5%, which are about four times that of the pure non-bonded PVdF membranes. Apart from this, the bonded PVdF/PVB membranes express integrated properties of high water vapor transmittance rate (10.6 kg m(-2) d(-1)), modest air permeability (9.8 mm s(-1)), and good waterproofness (58 kPa). Furthermore, the convenience and efficient of this fabrication process will allow for large-scale production of PVdF/PVB breathable-waterproof nanofibrous membranes with robust mechanical performance and board applications.