This paper presents an investigation on the surface roughness of burnished hypereutectic Al-Si alloy - a widely used light-weight and wear resistant material in automobile, electric and aircraft industries. Based on the techniques of Taguchi, an orthogonal experiment plan with the analysis of variance (ANOVA) is performed and a second-order regressive mathematical model is established. Meanwhile, the influence of process parameters on surface roughness and its mechanism are discussed. From the experiments, it is found that burnishing process is effective to decrease surface roughness of hypereutectic Al-Si alloy components, in which, all input parameters have a significant effect on the surface roughness. To achieve a small surface roughness, the optimum process parameters are recommended.