In-plane flow of fluid in needle punched nonwoven webs was characterized in terms of permeability. The permeability was measured by using GATS (Gravimetric Absorbency Testing System). The variables considered in the experiment were fiber type, fluid type, needling conditions and environmental pressure. Simple structural model was introduced to derive the mean hydraulic pore size which provided criteria for analysis of experimental data. Understanding the mean pore size derived in this research will be useful in structural design of absorbent products of the low thickness such as diaper, sanitary napkin, medical wiper, and so on.