Oil spills cause serious ecological threats to aquatic life. High-performance polymer composite films using biomass fibers for rapidly removing oil from wastewater are exceptionally attractive due to sustainable development and high efficiency. Herein, we report a novel polymer composite film composed of polyurethane (PU) and biomass-based Juncus effusus (JE), which was fabricated using the nonsolvent induced phase separation method. The Juncus effusus/polyurethane (JEPU) composite films exhibited a highly controllable porous structure with the addition of JE powders. Owing to the strong hydrogen-bond interactions between biomass JE and PU matrix, the JEPU composite films showed good interface compatibility and enhanced mechanical property. Tensile stress-strain measurements demonstrated that the 2%JEPU showed tensile strength and strain of 1.14 MPa and 280.61%, respectively. Furthermore, the JEPU composites possess desirable hydrophobicity/oleophilicity with a water contact angle of 127°, exhibiting a good oil absorption capacity. The developed JEPU composite films may broaden the application range of industrial crops and products in eliminating oil contaminants from water.