This expemment was carried out to investigate the effect of mating type(LY×D, LY×L. LY×Y and LY×DH), parity(1st and over 2nd) and weaning age(32 days and 28 days) on reproductive traits for litter size, pig and litter weight at birth and at weaning. The 155 piglets were produced from mating systems breeding Landrace×Yorkshire sows to Duroc boars. Landrace×Yorkshire sows to Landrace boars, Landrace×Yorkshire sows to Yorkshire boars and Landrace×Yorkshire sows to Duroc×Hampshire boars. The effects of parity and weaning age were also studied on the sow`s body condition for changes in backfat thickness and sow`s weight during the lactating periods arrd days to rebreeding of 16 sows produced by crossbreeding Landrace sows to Yorkshire boar. For the body conditions of sows during lactating periods, it was not significantly different by parity and weaning age. but average thickness of backfat was reduced by 4mm and average body weight loss was about 26㎏. Days to rebreeding of sows was about 6 days. For the litter size at birth and weaning, it was to be the highest at 1 I piglets in the LY×L, but the lent at 8 piglets in the LY×DH among the mating types. Pig weight at birth was the highest at 1.64㎏ in the first parity of LY×DH mating type and was the lightest at 1.25㎏ in the first parity of LY×D mating type. Pig weight at weaning was the highest at 9.65㎏ in the second parity of the LY×Y mating type and was the lightest as 5.1㎏ in the first parity of the LY×D mating type.