When an object is observed, not only its colour but, primarily, its overall appearance is noticed that Luster is one of the best important effective properties of appearance fabric Luster is usually described visually, that is not very accurate. Luster means sum intensity of angular and diffiuse reflection of a material surface. Luster measures in this study via image Analysis, that according to last researchs is the best methods. We measure Luster index of twenty seven weft khitted fabrics with varying stitch density and texture styles and effect of structural parameters of fabric is investigated. As stitch density decreases, according to resulting in this study, luster increase. Also single jersey textures and textures with missed loops have most and interlock textures and textures with knitted loops have least luster index values. Comparing between luster and gloss, we can find inverse relation. Also air permibility and friction cofficient have most and least effect on weft knitted fabrics luster.