To investigate relationship between birth-weight of parents and fetal macrosomia and its genetic susceptibility. A case-control study with 237 macrosomia and 257 normal birth-weight babies was conducted to retrospectively analyze their parents' birth weight and mothers' conditions during pregnancy. Multivariate non-conditional logistic regression analysis showed that risk of macrosomia increased with increase in maternal birth-weight (OR = 1. 707, 95% CI: 1. 145 - 2. 545) and paternal birth-weight (OR = 1.979, 95%CI:1.306 -2.998). Macrosomia is fetal obesity and related to multi-gene susceptibility with heritability of 74.48%. Maternal effect on macrosomia may come from her obesity gene and intrauterine condition, while paternal effect mainly exhibits by his obesity gene carriage.