OBJECTIVE To evaluate birth weights (BW) in late preterm infants (LPI) with different gestational ages (GA) and their physical growths at correct ages (CA) 1, 3 and 6 months. METHODS A total of 287 LPIs were recruited for a cohort study between May 2010 and September 2011. Birth weights (BW) in infants with different gestational ages and their physical growths at CA 1, 3 and 6 months were evaluated. RESULTS Of the 287 LPIs, mean BW in LPIs with gestational ages of 34-34(+6) and 35-35(+6) weeks was significantly lower than the reference value from a physical growth investigation on newborns of 15 cities of China in 1986 (P<0.05). However, mean BW in singleton LPIs (n=128) with gestational ages of 36-36(+6) weeks was significantly higher than the reference value (P<0.05). At CA 1, 3 and 6 months, more than 90% LPIs reached P(3) level in weights for age, length for age and head circumference for age. At CA 1 and 3 months, weight for age and head circumference for age in the LPIs were statistically higher than the reference values of physical growth in children under 7 years from nine cities of china in 2005 (P<0.05). Mean length for age at CA 1, 3 and 6 months was not significantly different from the reference value. CONCLUSIONS There are obvious differences in BW in the LPIs compared with the reference value from a physical growth investigation on newborns of 15 cities of China in 1986, suggesting that the reference value of BW at different gestational ages needs to be updated in a certain interval. Before CA 6 months, there is a risk of overweight in LPIs and long-term monitoring is necessary. Growth of length should be followed-up for a long time.