Abstract: Battery separators, as the key components of energy-storage devices, are crucial for determining the safety and lifespan of batteries. Commercial separators are primarily produced via dry and wet processes. Generally, separators produced by dry processes have low porosity and a heterogeneous pore distribution, and they possess good mechanical strength owing to their tensile-oriented crystallization mechanism. Dry-processed separators are usually applied in portable electronic products with low operating voltages and small current output requirements. To their disadvantage, the dry process requires high-precision instrumentation, high-quality raw materials, and is energy-intensive, which raises the threshold of production technology. In comparison, separators produced by wet processes using thermally induced phase separation are complex to produce and have poor mechanical strength. Separators suitable for power transmission equipment require high porosity and electrolyte uptake. The development of a separator that combines the advantages of both the dry and wet processes, exhibits good mechanical properties, high porosity, uniform pore distribution, and is suitable for high-performance batteries with long lifespans, remains a significant challenge. Moreover, the key technologies and equipment for fabricating high-quality separators are not yet sustainable. Therefore, a novel process for producing high-quality separators that are readily mass-produced is urgently required. Herein, a novel “blow molding–extraction” process is introduced for the development of high-performance separators. This process effectively integrates the key steps of the dry and wet processes, including melt mixing, extrusion blow molding, gas inflation, longitudinal stretching, and cooling. The integration of the dry and wet processes can be learned from mature theories and technologies in blow-molding film and separator production, which would shorten the research cycle. More importantly, the equipment required to prepare this separator is a traditional inflation film-manufacturing machine, which is inexpensive and can realize the large-scale preparation of films. In this study, we obtained more than ten square meters of film in a single experiment. In addition, the mechanical properties of the blow-molded film were enhanced via gas-blowing-induced double-oriented crystallization. For separators prepared via a wet process, the removal of pore-forming agents from the film and solvent recycling are very mature processes. First, separators with a porosity of 63% and an excellent electrolyte uptake rate of 115% were produced by adjusting the component ratios and selecting appropriate pore-forming agents. Furthermore, the introduction of the extraction process resulted in a uniform microporous structure that significantly enhanced the ionic transport efficiency of the electrolyte to yield ionic conductivity of 0.23 mS·cm^?1. The assembled batteries demonstrated high capacity and excellent cycle stability. These findings suggest that the “blow molding–extraction” process not only improves the overall performance of the separator but also provides a novel technological pathway for manufacturing high-end lithium battery separators with significant academic value and application potential. This method establishes a solid foundation for future advancements in battery technology and fosters further research and applications in the domain of electrochemical energy storage.