Objective：To study the effect of different amniotic fluid index on pregnancy outcome in full-term pregnancy. Methods：Five hundred and seventy two full-term pregnant women whose amniotic fluid index（AFI） were less than 80mm were selected as the experimental group，and 599 full-term pregnant women whose AFI was more than 81mm but less than 250 mm were selected as the control group. All the experimental subjects were chosen from Chongqing Medical University Affiliated University Town Hospital since 2014 to 2018. The two groups excluded high-risk obstetric factors，such as cephalopelvic disproportion，scarred uterus，previa placenta，abnormal placenta orientation and twin pregnancy，etc.. Groups were divided according to the AFI（mm） of 0-30，31-50，51-65，66-80. Then the cesarean section rates due to abnormal NST or OCT positive in each group were calculated and analyzed combined with the data of the group of 81-250. Results：The cesarean section rates of the group 0-30，31-50，51-65，66-80 and 81-250 were 79%，55%，47%，44%，44%，respectively. All pregnant women in the groups have a smooth delivery，and no newborn baby has been stifled to death. Comparative analyses of the Chi-square test and group to group comparison by using SPSS 20.0 showed that：the cesarean section rate was not all the same among the five groups（P<0.05）；there was no significant difference between 0-30 and 31-50 groups（P=0.05）；there were significant differences between 0-30 and 51-65 groups（P<0.05），0-30 and 66-80 groups（P<0.05），0-30 and 81-250 groups（P<0.05）；there was no significant difference between 31-50 and 51-65 groups（P>0.05）；there were signifi－cant differences between 31-50 and 66-80 groups（P<0.05），31-50 and 81-250 groups（P<0.05），31-50 and 66-80 groups（P<0.05），31-50 and 81-250 groups（P<0.05）. There was no significant difference between 51-65 and 66-80 groups（P>0.05），51-65 and 81-250 groups（P>0.05），66-80 and 81-250 groups（P>0.05）. Conclusion：The amniotic fluid index of 80 mm and 50 mm has definite guiding significance，while more detailed grouping of amniotic fluid volume has no obvious guiding significance for clinical work in this study.