Objective To investigate the catch-up growth of preterm infants within a corrected age of 6 months and the risk factors for extrauterine growth retardation (EUGR). Methods A total of 321 preterm infants who were discharged after treatment in the neonatal intensive care unit and had regular follow-up documents with complete follow-up records were enrolled. According to the Prenatal Health Care Norms in 2015, these infants were divided into low-risk group with 69 infants and high-risk group with 252 infants. The Z-score method was used to evaluate body weight, body length, and head circumference, and the catch-up growth of the preterm infants within a corrected age of 6 months was analyzed. A multivariate logistic regression analysis was performed to identify the risk factors for EUGR at the corrected age of 6 months. Results The percentage of preterm infants with Z scores of body weight, body length, and head circumference of < -2 (not reach the standard for catch-up growth) in both groups decreased gradually with increasing corrected age. At the corrected age of 6 months, the percentages of preterm infants whose body weight, body length, and head circumference did not reach the standard for catch-up growth in the low-risk group were reduced to 1.4% (1/69), 2.9% (2/69), and 1.4% (1/69) respectively, while in the high-risk group, these percentages were reduced to 1.2% (3/252), 1.6% (4/252), and 3.6% (9/252) respectively. The high-risk group had a significantly higher incidence rate of EUGR at the corrected age of 6 months than the low-risk group (28.2% vs 15.9%, P=0.039). The multivariate logistic regression analysis showed that multiple birth (OR=2.68, P=0.010), low birth weight (<1 000 g: OR=14.84, P < 0.001; 1 000-1 499 g: OR=2.85, P=0.005), and intrauterine growth retardation (IUGR) (OR=11.41, P < 0.001) were risk factors for EUGR at the corrected age of 6 months, while nutritional enhancement after birth (OR=0.25, P < 0.001) reduced the risk of EUGR. Conclusions Most preterm infants can achieve catch-up growth at the corrected age of 6 months. High-risk preterm infants have a high incidence rate of EUGR at the corrected age of 6 months. Multiple birth, low birth weight, and IUGR are risk factors for EUGR, while rational nutritional enhancement after birth can reduce the incidence rate of EUGR in preterm infants.