Core-spinning was done by introducing the filament yarn under tension into the drafted strand as the latter entered the front roller of the ring spinning frame(spintester). A 100 den-24 nylon filament yarn(11.11 tex-24 fils) was used as core and SM-1 inch cotton was used as sheath. The effects of twist multiplier and weight ratio of core-sheath on the covering property of sheath was investigated. It was found that the twist multiplier of core-spun yarn gave the effect on the covering property of the sheath in the mean while the weight ratio of core-sheath did not give the effect on the covering property of sheath.