【Objective】 To investigate the effects of feeding in different ways on physical development and serum index of preterm infants. 【Methods】 91 preterm infants whose birth weights were all above 1 500 g. Infants were divided into 5 groups by following feeding ways: preterm-infant formula; term-infant formula; preterm-infant formula and breast milk; breast milk; term-infant formula and breast milk. Weights, lengths were measured at 4~6 months adjusted by gestational age.Z-score of weights and lengths were calculated. Serum total protein, albumin, and micronutrients etc were detected. 【Results】 The Z-score of weights and lengths in Group 4 were blow zero, and lower than other groups. But the differences were not significant (P>0.05). The serum levels of BUN in Group 4 was significant lower than other groups (P<0.05) and was significant higher in Group 2 than Group 3, Group 4, Group 5 (P<0.05). The serum levels of albumin in Group 1 and Group 5 were significant higher than other groups (P<0.05), but were similar between the two group (P=0.947). There were no significant differences in other serum index levels among the groups (P>0.05). The levels of serum BUN were correlated with the Z-score of length (r=0.228, P=0.04). 【Conclusion】 1) Exclusive breast feeding can not provide enough nutrients for matching the early growth and development of preterm infants; 2) Further study will be needed to investigate the mechanisms and long effects of high serum BUN levels in preterm infants feeding with term-infant formula.