Abstract: In order to address the surface quality issues in the grinding of QT500 ductile iron, systematic grinding experiments were conducted. This study investigated the effects of grinding direction (down-grinding and up-grinding), grinding depth (a_p), and relative linear speed ratio (i) on the surface roughness of the workpiece. The results indicated that grinding depth is the most significant factor influencing surface roughness, which increases as the grinding depth increases. The influence of grinding direction on surface roughness is closely related to grinding depth: at small grinding depths, up-grinding results in lower surface roughness than down-grinding, whereas the opposite is true at large grinding depths. The effect of the relative linear speed ratio on surface roughness varies depending on the grinding depth. At small grinding depths, the surface roughness first increases and then decreases with increasing relative linear speed ratio; at large grinding depths, the surface roughness continuously decreases. By analyzing the micro-morphology of the ground surfaces, this study revealed the material removal mechanisms under various grinding parameters. The best surface quality was achieved under up-grinding conditions with a grinding depth of 0.01  mm and a relative linear speed ratio of 2 625, providing a theoretical basis for improving the grinding quality of QT500 ductile iron.