<p>The pia-arachnoid complex (PAC), functioning as a critical biomechanical interface between the skull and brain, requires precise dynamic characterization to improve traumatic brain injury (TBI) prediction under impact loading. However, existing mechanical data for PAC under high-strain rate conditions remain scarce due to experimental challenges posed by its ultra-thin and low stiffness. Conventional metallic split Hopkinson bar systems encounter extremely weak signals when testing this tissue. In this study, we present the first high-strain rate dynamic tensile characterization of PAC. To address the challenge of weak transmission signals, a double-bullet electromagnetic driven split Hopkinson stretch bar system with polycarbonate bars was used. Three dynamic tensile tests were conducted at varying strain rates, achieving a maximum strain rate of 1800 s⁻¹. Experimental results reveal significant strain rate sensitivity and nonlinear stress-strain behavior. A rate-dependent constitutive model for PAC was established based on the Yeoh hyperelasticity model and the Bernstein-Kearsley-Zapas viscoelastic theory. Model parameters were optimized using a hybrid approach combining particle swarm optimization and genetic algorithm. The proposed constitutive equation effectively captures the strain rate sensitivity and nonlinear mechanical characteristics of PAC across a wide range of strain rates. The measured dynamic properties and validated constitutive model provide essential biomechanical data for PAC, thereby advancing the predictive capability of TBI simulations under high-speed impact conditions.</p>