Abstract: Objective: To evaluate the relationship between maternal pre-pregnancy overweight/obese status and offspring attention deficit hyperactivity disorder(ADHD). Methods: The Chinese and English databases, including CNKI, Wanfang Data, Sinomed, PubMed, Embase, and Cochrane library, were searched for cohort studies on the association between maternal overweight/obese status before pregnancy and offspring ADHD from the time of establishment to 11th February, 2020. The retrieving methods combined Mesh subject terms and free terms related to maternal pre-pregnancy BMI, offspring ADHD and cohort. Two researchers did the primary and full-text selection and extracted data individually. Pre-pregnancy BMI was the only indicator for the classification of being underweight, normal, overweight and obese. ADHD evaluation scale was filled by teachers or parents, and inattention, hyperactivity/impulsivity or combined type of ADHD were counted. Exposure factors of different cohorts were extracted. Newcastle-Ottawa scale (NOS) was used for quality assessment. Data analysis was performed by Stata 15.0. Results: A total of 13 studies were included in this study with 16 cohorts and 12 of them were prospective cohort studies. A total of 801,834（511-649,043，median 3,803）subjects were recruited. The results of the meta-analysis showed that both of being maternal overweight (OR=1.21, 95%CI:1.16-1.27, I2=18.3%) and obese (OR=1.35, 95%CI: 1.19-1.55, I2=84.0%) were significantly associated with offspring ADHD, while being maternal underweight was not significantly associated with ADHD (OR=1.05, 95%CI: 0.97-1.13，I2=0%）. Heterogeneity analysis results showed that: a. Regional subgroup analysis revealed the results of being pre-pregnancy overweight and obese in European and North America cohort was OR=1.22（95%CI, 1.19-1.26），OR=1.45（95%CI, 1.31-1.61）and OR=1.14（95%CI, 0.85-1.52），OR=1.94（95%CI, 1.05-3.58）, respectively. b. Subgroup analysis based on offspring age (preschool, school age and not given) indicated pre-pregnancy obesity was not related to increased risk of preschool ADHD. c. Subgroup analysis based on ADHD clinical types revealed that being pre-pregnancy overweight and obese increased the risk of combined ADHD (OR=1.22, 95%CI: 1.19-1.25，OR=1.41, 95%CI: 1.22-1.63) and pre-pregnancy overweight status increased the risk of inattention ADHD (OR=1.40, 95%CI: 1.06-1.87). There was no publication bias by the Begg rank correlation test and the Egger linear regression test. Conclusion: This meta-analysis suggests that maternal pre-pregnancy overweight/obese status may increase the risk of ADHD in offspring while maternal pre-pregnancy underweight status may not.