Moisture permeability is an important property of cotton fabrics. Fully understanding of cotton fabric moisture absorption and moisture permeability plays an important role in the further study of the cotton fabric property and development of new cotton fabric. According to 6 kinds of cotton fabrics, the moisture permeability was measured by wet cup moisture absorption method under normal temperature. Such structural parameters have been analyzed as the yarn density, warp and weft density, weight per square meters, thickness, twist, which influenced the moisture permeability of fabrics. By the grey relational analysis, the grey relational sequence of structural parameters have been concluded which affect the moisture permeability of fabrics: thickness>weight per square meters>weft density>weft twist>warp density>wefts yarn density>warp twist>warp yarn density. The results provide theoretical basis for research and designing of textile products and modification of fabrics.