Gestational age and birth weight are supposed to associate with childhood blood pressure but remains unclear. This study aimed to investigate the association between gestational age, birth weight, and blood pressure among Chinese children. In all, 49 357 children aged 6-18 years were included from a nationwide survey in China. Gestational age, birth weight, and socioeconomic data were collected by questionnaires. Systolic (SBP) and diastolic (DBP) blood pressure were objectively measured. The associations between birth measures and blood pressure were examined by multivariable linear regression and logistic regression. The prevalence of hypertension was 19.1%, 19.2%, and 21.0% in preterm, term, and post-term subgroups, and 20.1%, 19.1%, and 19.8% in low-, normal-, and high-birth-weight subgroups, respectively. Results showed significantly positive associations of gestational age with SBP, DBP, SBP z-score, and DBP z-score in the overall and term subgroup, but not in the preterm or post-term subgroup. Birth weight was inversely related to SBP, DBP, SBP z-score, and DBP z-score across the entire birth-weight spectrum, and the overall association was stronger in girls than in boys. Similar associations were found in diffident age subgroups. Children with high birth weight had decreased odds of hypertension (OR 0.84, 95% CI 0.77-0.92) after adjustment for covariates. Preterm birth increased the risk of high SBP only in boys. This study suggested that gestational age was positively associated with blood pressure only in term-born children. Birth weight had a negative association with childhood blood pressure across the whole range of birth weight.