Waterproof and breathable membranes that provide a high level of protection and comfort are promising core materials for meeting the pressing demand for future upscale protective clothing. However, creating such materials that exhibit environmental protection, high performance, and ease of fabrication has proven to be a great challenge. Herein, we report a novel strategy for synthesizing fluorinated polyurethane (C6FPU) containing short perfluorohexyl (-C6F13) chains and introduced it as hydrophobic agent into a polyurethane (PU) solution for one-step electrospinning. A plausible mechanism about the dynamic behavior of fluorinated chains with an increasing C6FPU concentration was proposed. Benefiting from the utilization of magnesium chloride (MgCl2), the fibrous membranes had dramatically decreased maximum pore sizes. Consequently, the prepared PU/C6FPU/MgCl2 fibrous membranes exhibited an excellent hydrostatic pressure of 104 kPa, a modest water vapor transmission rate of 11.5 kg m-2 d-1, and a desirable tensile strength of 12.4 MPa. The facile fabrication of PU/C6FPU/MgCl2 waterproof and breathable membranes not only matches well with the tendency to be environmentally protective but also fully meets the requirements for high performance in extremely harsh environments.