Objective To understand the dietary behavior of middle school students in Urumqi and the relationship between dietary behavior and obesity,in order to guide the reasonable dietary behaviors of middle school students and provide basis for healthy growth. Method A total of 3 458 middle school students from 72 classes in 4 schools in Urumqi were randomly selected to complete the questionnaires by cluster sampling method in May 2016. Results The rates of eating fresh fruit frequently(87.6% vs. 54.3%),eating sweet snacks frequently(61.2% vs. 51.5%),eating vegetables frequently(93.5% vs. 91.2% ),dislike eating certain food (61.2% vs. 51.5%)in girls were significantly higher than those in boys (P<0.01). The rates of eating fresh fruit frequently(87.5%vs. 55.0%),having milk frequently(72.4%vs. 65.7%),having breakfast(86.2%vs. 83.4%) in Han students were significantly higher than those in ethnic minority students(P < 0.05).Multi-factor analysis showed that boys (OR=1.44,95% CI: 1.09~1.88),poor eating habits (OR=1.43,95% CI: 1.11~1.89),and often eating food at a roadside stall (OR=1.34,95% CI:1.08~1.73) were risk factors for overweight and obesity in middle school students. Conclusions The unhealthy eating habits of middle school students are related to obesity. It is supposed to strengthen health education on the good diet behavior to middle school students in order to promote their healthy development.