Abstract: To mitigate issues of traditional emulsified asphalt in road engineering applications, such as easy cracking at low temperatures and insufficient tensile properties, hydroxypropyl methyl cellulose-waterborne polyurethane modified emulsified asphalt (HPMC/WP-MEA) composites were prepared by a high-speed shearing method. This work investigates the effects of waterborne polyurethane (WPU) dosage, shear rate, and hydroxypropyl methyl cellulose (HPMC) dosage on the tensile properties of the composite, as well as the underlying enhancement mechanisms, based on methods including force ductility tensile performance parameter design, fourier transform infrared spectroscopy, bending beam rheometer (BBR) tests, and correlation coefficient analysis. The results indicate that the WPU dosage exhibits a strong correlation with the viscosity-toughness of WP-MEA. When the WPU dosage reaches 2%, WP-MEA demonstrates better tensile properties. The shear rate has a relatively small impact on the overall tensile properties of WP-MEA, but an excessively high shear rate will destroy the molecular structure of WPU, thereby reducing the toughness of WP-MEA. HPMC significantly affects the tensile properties of HPMC/WP-MEA composites, and the bridging effect of HPMC can enhance the viscosity-toughness of HPMC/WP-MEA. It is recommended that the dosage of HPMC be 1‰-2‰. Through the preparation, analysis, and characterization of the tensile properties of HPMC/WP-MEA composites, this work lays a certain theoretical foundation for the research and development as well as performance optimization of high-performance and low-pollution emulsified asphalt composites.