Objective: To investigate the current situation of obesity and related metabolic abnormalities among preschool children, so as to provide theoretical support for future intervention. Methods: A cohort of 3 952 children, born in Tianjin and enrolled in the kindergarten from September 2017 to October 2018, were selected to conduct a baseline survey and a three-year follow-up (questionnaire survey, physical examination and laboratory testing). At the same time, a two-way cohort study was conducted to retrospectively collect maternal prenatal examination, delivery and regular physical examination information of children from birth to preschool age from Tianjin Maternal and Child Health Information System. Results: A total of 3 935, 3 654 and 2 739 children completed the follow up in the primary, middle and senior classes of kindergarten respectively. The height and weight of pre-school children increased with age, while the percentage of body fat decreased with age ( β-trend =-0.74, P <0.01). During three-year follow up, height, weight and body mass index of boys were higher than girls (P<0.05), while the percentage of body fat was lower than girls (primary class: 17.5%,18.5%; middle class: 16.4%,17.2%; senior class: 16.1%,17.1%, P <0.05). The detection rate of overweight (including obesity) and obesity increased with age( χ 2 trend were 15.51,38.72, P <0.05). The total detection rate of obesity increased from 5.4% at the baseline level to 9.6%. Laboratory test results showed that the detection rates of fasting blood glucose of boys were higher than that of girls in primary class, but blood lipid abnormalities were in the opposite (glucose: 7.7%, 4.8 %; lipid: 23.8% , 27.7%)( χ 2=12.01, 6.63, P <0.05). Conclusion The study has established a large growth cohort starting from the early embryonic stage, which will help to establish the strategies to promote children s health and prevent obesity and chronic diseases from multidimensional perspectives.