This research studies the effect of the extension increase % of bare spandex yarns during loop formation and also effect of fabric softener treatment on properties of plain jersey fabric made of cotton and spandex yarns. Samples with 100% cotton yarns, spandex yarns in alternating courses (half plating) and spandex yarns in every courses (full plating) were produced on a circular knitting machine where the two latter cases were produced at five different levels of the spandex extension. Thermal setting was carried out without any traverse tension during finishing to evaluate the full effect of spandex extension. After dyeing process, fabrics were treated two different fabric softener types cationic, silicon and two concentrations %. Results showed that there is a sharp increase in courses density rather than wales density, fabric thickness and weight per unit area were also increased with considerable decrease in air permeability in the case of half and full plating.