Abstract: In order to investigate the effect of hole diameter in honeycomb preform on the W diffusion uniformity, the WC/Fe composites with different diameters were fabricated by vacuum expendable pattern casting (V-EPC) process. Based on the W mass fraction distribution analysis, it is found that the W distributes uniformity when the hole diameter is too large or too smallthe, while wear resistance of WC/Fe composites with the proper hole diameter of preform is the best, and the differences of the W mass fraction and hardness between initial hole wall and initial hole center are reduced. The simulation results by diffusion dynamics show that the uniformity of W diffusion is both influenced by diffusion distance and diffusion time. The W diffusion is limited when the hole diameter is samll and the diffusion distance is short although the diffusion time decreases, resluted from the fast internal matrix solidification. The W diffusion is also limited when the hole diameter is large, although the internal matrix solidifies slow and the diffusion time increases, but the diffusion distance increases. So the proper hole diameter has positive influence on the W diffusion uniformity with reasonable diffusion distance and diffusion time. On the contrary, the W diffusion uniformity is undesirable, and the W mass fraction and the hardness at the initial hole center are lower, resulting in the reduction of wear resistance within a certain range.