Objective To investigate the physical and mental development of small and appropriate for gestational age preterm infants in their early life. Methods This study recruited 220 preterm infants, who were discharged from our hospital and visited preterm following-up clinic at regular intervals from February 2009 to December 2012. All of those infants were divided into two groups based on whether their birth weight below 10th percentile for their gestational ages or not. Weights, lengths and head circumferences were measured up to seventh month age adjusted by gestational age. Meanwhile, mental tests were conducted by the professional staffs working on the children developmental assessment at their adjusted months of 5th, 6th or 7th. All of physical and mental scores were compared between the two groups. Results The SGA group was statistically less than the AGA group on the Z-score of weights from the ifrst to sixth month adjusted by gestational age (P<0.05). The difference disappeared on the seventh adjusted month age (P>0.05). The SGA group was statistically less than the AGA group on the Z-score of lengths from the ifrst to iffth month adjusted by gestational age (P<0.05). The difference disappeared on the sixth and seventh adjusted month age (P>0.05). The SGA group was statistically less than the AGA group on the Z-score of head circumferences from the ifrst to seventh month adjusted by gestational age (P<0.05). The SGA babies scored statistically less than the AGA babies with a mean development quotient score of 96.7 and 102.9, respectively (P<0.05). The scores of movement, cognitive, language in the SGA group were statistically less than those in the AGA group(P<0.05). Conclusions Preterm SGA could achieve satisfactory weight catch-up gain, with a decreasing difference from preterm AGA while they were getting older. But the length catch-up growth of preterm SGA seemed unsatisfactory with a big differece from preterm AGA. There was the worst catch-up on head circumference in those preterm SGA, backward in mental development, particularly in their movement, cognitive and language capacity.