Pulsed compression gratings are critical optical components for the development of high-energy lasers. However， laser manufacturing processes often generate surface contaminants and microstructure defects， leading to technical challenges limiting the advancement of high-power laser systems. To improve the laser-induced damage thresholds of gratings， a novel method involving magnetic compound fluid polishing for pulse compression gratings was developed herein. The microscopic structure， surface morphology， surface roughness， diffraction efficiency， and laser-induced damage thresholds of grating samples were evaluated before and after polishing. This assessment allowed a comparison of the grating surface quality and performance before and after polishing. Consequently， the magnetic compound fluid polishing process was found to effectively minimize burrs and microstructure defects generated during the manufacturing process without damaging the intrinsic grating structure. After 3 min of polishing， the grating surface roughness decreased from 21.36 nm to 3.73 nm. Furthermore， the laser damage threshold increased from 2.8 J/cm² to 3.8 J/cm²， improving the laser damage resistance by 35.7% without influencing the diffraction efficiency. These results demonstrate that magnetic compound fluid polishing is a highly effective method for enhancing the surface quality and overall performance of grating components.