ObjectiveTo identify and analyze the possible influencing factors of obesity among public primary school students in Minhang District， Shanghai. MethodsBasic data， collected through questionnaire stars， was imported with merged physical examination data into Excel to form a database. Data were collected by questionnaire and analyzed by SPSS 22.00. Independent sample t-test was used for the data with normal distribution. Nonparametric test was used for the data with non-normal distribution. χ² test was used for the quantitative data. Logistic regression was used for univariate and multivariate analysis. ResultsAccording to the national physical health standards for students （revised in 2014） ， the prevalence rate of obesity among primary school students in Minhang district was 29.63% . The prevalence of overweight and obesity was 32.1% in boys and 26.9% in girls. The trend of overweight and obesity in different grades was similar among different genders .A single factor analysis showed that， being the only child （χ²=9.300， P<0.01） ， father obesity（χ²=106.417， P<0.001） or mother obesity（χ²=118.534， P<0.001） ， mother's overweight during pregnancy （χ²=159.731， P<0.001） ， caregiver's role as grandparents （χ²=38.736， P<0.001） ， low education level （χ²=111.309， P<0.001） had effects on overweight and obesity of children while the differences had statistical significance. Pupil's bad eating habit （χ²=18.905，P<0.001） and preference （χ²=22.901， P<0.001） ， insufficient sleep time （χ²=61.685， P<0.001） ， long-time using of electronic products （χ²=37.182， P<0.001） and low-time of exercise （χ²=15.328， P<0.001） also affected the obesity of primary school students. Among the five factors of family， diet， psychology， static state and dynamic state， the influencing factors of obesity in primary school students from grade one to grade four were being the only child， obese father and/or mother， overweight mother during pregnancy， caregivers without higher education. In terms of diet， it was mainly based on eating habits before bedtime， as well as partial and picky eating habits. In terms of psychology， the main psychological source was the pressure of learning in school. There was a clear relationship between the pace of learning and not keeping up. Static analysis revealed a correlation with lack of sleep. After assigning values based on eye hygiene recommendations for the use of electronic products， it was found that there was no direct correlation between obesity in primary school students and the duration of electronic product use. Dynamic analysis showed that not taking part in school physical exercise was related to obesity. ConclusionThe obesity of primary school students is influenced by family， diet， psychology， static and dynamic factors. The intervention of obesity in primary school needs the joint efforts of school， society， family， self-cognition and so on.