This study aims to address the low cleaning efficiency (73.12%) and high cotton loss rate (12.50%) of existing stripper-and-stick cleaners when processing machine-harvested long-staple cotton. Based on the material characteristics of Xinjiang long-staple cotton, a novel impurity removal device was designed specifically for its cleaning. A mechanical model of cotton–impurity interaction was established to guide the design of U-shaped saw cylinder parameters. Static analyses conducted via Ansys Workbench revealed that both straight and arc-shaped sawteeth exhibited negligible deformations (≤4.73 × 10⁻⁴ mm) and von Mises stresses (≤9.52 MPa), meeting the practical operational requirements. Through orthogonal experiments (sawtooth type, linear velocity, and feed speed), the optimal operating parameters were determined as arc-shaped sawteeth, 7.5 m/s linear velocity, and 11 t/h feed speed. Prototype testing demonstrated that under these parameters, the impurity removal device achieved an average cleaning efficiency of 82.42% (a 9.30% improvement over conventional devices) and an average cotton loss rate of 8.34% (a 4.16% reduction compared to conventional devices). This study provides a valuable reference for the design and optimization of stripper-and-stick cleaners specifically tailored for machine-harvested long-staple cotton.