Objective To examine the catch-up growth during infancy in preterm and low birth weight infants. Methods A total of 252 preterm and low birth weight infants who received physical examination in children's health clinic during Jan. 2013 to Dec.2016 were enrolled in this study.Weight and length of infants at birth and 1 year old expressed as standard deviation scores and catch-up growth was defined as an increase of 0.67 in the Z scores between birth and the age of 1 year old.The difference of catch-up growth between boys and girls was evaluated. Results Among 252 preterm and low birth weight infants,there were 118 male infants(46.8%) and 134 female infants(53.2%).The rapid growth of weight[Z:(1.41±0.83)kg] and length[Z:(0.82±0.76)cm] occurred infants during infancy.The rates of catch-up growth for weight and length were 80.5% and 62.7%,respectively;There were no differences on catch-up growth for weight and length between male and female infants (χ²=1.583,1.082,P>0.05).The rate of catch-up growth for weight of children born appropriate for gestational age was higher than that of small or large for gestational age (χ²=8.552,P=0.014). Conclusions Catch-up growth occurs during infancy in most of preterm and low birth weight infants.Correctly nutritional support and growth monitoring are essential for growth development.