6061Al matrix composites reinforced by ZnO-coated Al18B4O33 whiskers were fabricated by a semi-solid mechanical stirring technique. The effects of ZnO coating on interfacial reaction between whiskers and matrix and the tensile properties of the composites were investigated. Tensile tests on composites were performed at room temperature, and microstructures were observed by scanning electron microscopy (SEM). The results show that the surface treatment of whiskers could reduce interfacial reaction effectively, improve the wettability between whiskers and matrix and enhance the tensile properties of the composites obviously. In addition, semi-solid stirring parameters were also under preliminary study. The stirring parameters were determined by the distribution of whiskers in the composites. The composites with homogeneously distributed whiskers were fabricated by semi-solid stirring at 610 ℃ for 30 min.