Objective　To research dynamic characteristics of neonatal intestinal flora and to analyze the related factors influencing the intestinal flora diversity by using polymerase chain reaction and denaturting gradient gel electrophoresis (PCR-DGGE) technology. Methods　Fecal samples were collected from 157 full-term and 72 pre-term neonates on the 3rd, 5th, 7th day and 3rd week after birth. The DNA samples of stool  were extracted and PCR amplification was performed on the variable regions 3 of the 16S rDNA gene. After analysis by DGGE, intestinal flora richness and Shannon-Wiener index were calculated and analyzed statistically according to the band present on the DGGE gel. Results　The neonatal intestinal flora richness  changed dynamically with time and increased with time during the observation period. Shannon-Wiener index raised with time within 7 d after birth. Intestinal flora richness and Shannon-Wiener index of the 5th day were significantly higher than those of the 3rd day after birth (P<0.001). Richness and Shannon-Wiener index of cesarean section group  were significantly lower than those of vaginal group on the 3rd day after birth (P<0.001). The number of vaginal group was also lower in Shannon-Wiener index on the 5th day after birth (P<0.05). Shannon-Wiener index of breast feeding group was significantly lower than that of formula feeding group on the both time of the 7th day and the 3rd week after birth (P<0.05). Full-term neonates' richness on the 3rd, 5th, and 7th day after birth and Shannon-Wiener index on the 3rd  and  5th day were significantly higher than those of pre-term infants. Conclusion　The intestinal flora diversity of neonates changed dynamically with time and the most dramatic development period was between 3rd and 5th day after birth. The intestinal flora diversity of cesarean section newborns was lower than that of vaginal delivery babies in the early period after birth. Breastfeeding diversity was lower than non-breastfeeding. Pre-term infants had low intestinal flora diversity and delayed colonization.