The purpose of present study was to explore the trajectories of growth of preterm and term infants of low, high, and appropriate birth weight. A total of 2465 infants were recruited from 2005 to 2007. Infants' length and weight were measured at 12 points: birth, 42 days, and monthly from 3 to 12 months. The catch-up growth of preterm infants, measured by weight or length of chronological age, occurred from 10th or 12th month of their lives. After adjusted gestational age, preterm infants' weight and length were caught-up from the adjusted birthday, overweight/over-length even occurred from 10th/11th month. For low birth weight term infants, catch-up growth was not found when using single weight or length. The ponderal index catch-up growth occurred earlier than measured by single weight or length. The catch-down growth of high birth weight term infants was not found in the first year of their lives.