Objective：To compare the weight growth of infants with different birth weight aged 0-6 months and to provide references for their clinical health care at early stage. Methods：Prospective cohort was established in the department of child health care in children’s hospital affiliated to Chongqing medical university from May 2010 to September 2011. The cohort was divided into the macrosomia group，the normal birth weight（NBW） group and the preterm low birth weight（PLBW） group. Infants with different birth weight were compared in terms of weight for age Z-score（WAZ），the incidence of overweight at 6th month and the weight growth speed from 0 to 6 months（ΔWAZ）. Results：（1）Respectively，86，154 and 107 examples were included in PLBW group，NBW group and macrosomia group. （2）At 6th month，the mean WAZs in PLBW group，NBW group and macrosomia group were（-0.60±1.12），（0.46±0.83） and （1.17±0.92），P＜0.000 1. （3）The mean ΔWAZs in PLBW group，NBW group and macrosomia group from 0 to 6 months were （2.41±1.01），（0.48±0.83） and （-0.56±0.95），P＜0.000 1. （4）The incidences of overweight in PLBW group，NBW group and macrosomia group at 6th month were 4.65%，6.49% and 19.63%. （5）In PLBW group，the mean ΔWAZ of preterm formula-fed infants and full term formula-fed infants was obviously higher than that of breast-fed infants，P=0.008 5；in NBW group and macrosomia group，the mean ΔWAZ of full term formula-fed was higher than that of breast-fed infants，but the differences were not significant. Conclusion：（1）A high weight growth level is maintained in macrosomia group and the incidence of overweight is the highest among three groups. The weight growth velocity is the lowest in macrosomia group compared with that of PLBW group and NBW group；（2）During the first 6 months of life，the weight growth velocity and overweight incidence are lower in breast-fed infants than in fomula-fed infants among the three groups.