Abstract: The high strain rate tensile mechanical property of Ultra-High Molecular Weight Polyethylene (UHMWPE) fibre bundles is normally measured via Split Hopkinson Tensile Bar (SHTB) test. There are two major technical matters in this test: firstly, how to effectively connect the flexible fibre bundles to high-strength SHTB steel rods, secondly, how to accurately measure tensile strain of the fibre bundles. This study designed thin sheet-like fibre bundle tensile specimen and specialized fixtures to efficiently connect the specimen to SHTB steel rods. In order to eliminate the interference of adhesives and fixtures on elastic longitudinal waves, the deformation of the fibre bundle was directly measured via Laser interference velocimetry. Tensile test was conducted on three-gauge length UHMWPE fibre bundles under strain rates from 290 s⁻¹ to 690 s⁻¹, and fracture process of the fibre bundles was recorded via high-speed camera. The results showed that: under high strain rate tension, UHMWPE fibre bundles exhibited significant size effects, and the fracture strength decreased with increasing gauge length; and the strain rate increased from 310 s⁻¹ to 690 s⁻¹, there was no significant correlation between UHMWPE fibre bundle fracture strength with the strain rate.