Main aim of this paper is to find a suitable model that makes possible the prediction of air permeability of a Knitting fabric on the base of its constructional parameters. The methodology: As the constructional parameters of Knitting fabric are considered: gouge of twist factor, yarn count yarns, diameters (or fineness) of yarns and a type of weave structures. This research is focused on clothing woven fabrics of a cotton type. Two variants of so-called cumulative parameter of a Knitting fabric structure are defined and they are applied on the set of Knitting fabrics. Porosities evaluated from empirical analysis and basic knitting wefts structural parameters (kind of material, yarn diameters and loop length / gouge setts). The cotton single jersey of weft knitting constant set of gouge and varying set of weft and varying yarn fineness are used for predictive model building. the obtained results, this new (EMP-THE) Empirical Theoretical Model of Volume Porosity and air Permeability in knitting fabrics are created end evaluated by the combination of partial of samples, numerical without graphs and suitable criterion expressing the predictive ability, a correlation between calculated values of structural parameters and experimental air permeability values was evaluated. Conclusions, in the first step the principal component analysis of volume porosity and air permeability in knitting fabrics, leading of new factors to the design suitable for end-use.