Abstract: Objective To investigate the effect of pre-pregnancy body mass index on STAT3-SOCS3 -leptin insulin signal pathway. Methods Ninety cases of newborns of obese/overweight pregnant women were selected as obese/overweight group, and 90 cases of newborn infants of pregnant women with normal body mass index were selected as normal group from January, 2016 to December, 2016 in Jiaxing Second Hospital. The newborn body mass index after birth 42 days, 6 months and 12 months were calculated. The blood leptin, fasting blood glucose, insulin, triglyceride, total cholesterol were detected. The expression of LepR, SOCS3, STAT3, IR, IRS1 mRNA levels were detected by reverse transcription-polymerase chain reaction (RT-PCR) assay. The LepR, SOCS3, STAT3, IR, IRS1 protein levels were detected by Western Blot. Results The body mass index of obese/overweight group infants at 42 days, 6 months and 12 months were higher than that of the normal group (P<0.05). At 12 months, the levels of serum leptin, fasting blood glucose, insulin, triglyceride and total cholesterol in the obesity/overweight group were higher than those in the normal group (P<0.05). The levels of LepR, STAT3, IR and IRS1 mRNA in the obese/overweight group were lower than those in the normal group (P<0.05), SOCS3 mRNA level was higher than that of the normal group (P<0.05); The protein levels of LepR, STAT3, IR and IRS1 in the obesity/overweight group were lower than those in the normal group (P<0.05), SOCS3 protein level was higher than that of the normal group (P<0.05). Conclusion Pre-pregnancy obesity/overweight affects the metabolic characteristics of offspring. The mechanism may be pre-pregnancy obesity/overweight affect STAT3-SOCS3-leptin insulin signaling pathway.