A mechanism-based analytical model for calculating the Degree of Pore-Opening (DPO) of porous metals processed via negative pressure infiltration method is developed. The emphasis is placed on predicting the dependence of DPO on the infiltration pressure difference, particle size, surface tension, and wetting angle between liquid metal and particles. Experimental measurements are subsequently performed to check the accuracy of model predictions, and it is shown that the proposed model can be used to quantitatively control the microstructure of porous metals during infiltration processing.