Porous metal fiber sintered felt is a type of new functional materials. This paper focuses on implementing the digital design of its multi-scale morphology. First, considering the self-affine fractal characteristics of the microtopography of machined metal surfaces, a previously developed mathematical method combining Weierstrass-Mandelbrot fractal geometry and triply periodic minimal surface is extended. In addition, the marching cubes algorithm is optimized according to the structure characteristics of sintered felt, so as to improve the efficiency of establishing its geometrical model. Meanwhile, a parameter representation method is introduced to drive the fractal TPMS model to adjust and control the morphology of sintered felt. The sample analyses warrant the higher efficiency of the proposed method and the ability of modeling and controlling multi-scale morphology of sintered felt. The effectiveness of the proposed model is also validated through numerical simulation and comparisons with other methods. The proposed approach can be directly used to describe the multi-scale morphology of other functional materials, thus facilitating the development of the corresponding numeric simulation technology.