Surface treatment of a Co-Cr-W-C based alloy by pack boronizing is performed in this study. Treating at temperatures between 950 and 1050oC for up to 5 hrs produces a layer-like boride coating. The phase and composition analysis of the boronized layer is carried out by means of optical and SEM, EPMA and XRD. The growth of overall boronized layer is observed to obey the parabolic law, suggesting that it occurs via a diffusion-controlled process. Along with the microstructural features of the boronized layer, some brief results of the improvements of the wear property of Co-Cr-W-C alloy by boronizing treatment are presented.