【Objective】 To investigate the prevalence and influencing factors of overweight and obesity among preschool children in Suzhou. 【Methods】 A stratified cluster random sampling method was used to select 24 452 children aged 3 - 6 years in different districts of Suzhou from December 2021 to June 2022. Then the prevalence rate of overweight and obesity was determined by physical measurements. A case-control study was conducted with a questionnaire survey of 3 786 children(1 893 in the obesity group and 1 893 in the control group) to analyze the factors influencing preschool obesity. 【Results】 1) The overall detection rates of overweight among preschool children in Suzhou was 14.8%(boys 14.6%, girls 15.0%). The overall detection rates of obesity was 7.9%(boys 8.7%, girls 7.1%), with a statistically significant difference between boys and girls(χ²=19.828, P<0.01). 2) There was statistically significant difference in the detection rates of obesity among different age groups(χ²=98.415, P<0.01), with the lowest rate in the 3 - 4 years old group(5.8%) and the highest rate in the 6 - 7 years old group(11.8%). 3) The overall detection rates of mild, moderate and severe obesity was 4.8%, 2.6% and 0.5%, respectively. The proportion of moderate and severe obesity significantly increased with age(χ²=57.275, P<0.01). 4) Risk factors for preschool obesity included birth weight >4 000g, cesarean section, parental overweight/obesity, strong appetite of children, eating speed <10min/meal, high frequency of fried food consumption(>1time/week), eating while watching television, sedentary behavior >2h/d, insufficient exercise endurance, screen time >1h/d, and late bedtime(after 21∶30)(P<0.05). Protective factors for preschool obesity included larger breakfast consumption, fruits and vegetables as regular snacks, and physical activity after meals(P<0.05). 5) Factors influencing the degree of preschool obesity included paternal overweight(OR=1.33, 95%CI:1.06 - 1.65), paternal obesity(OR=1.91, 95%CI:1.46 - 2.49), maternal overweight(OR=1.25, 95%CI:1.01 - 1.54), maternal obesity(OR=1.94, 95%CI:1.40 - 2.69), low education level of father(junior high school or below)(OR=1.57, 95%CI:1.25 - 1.96), strong appetite of children(OR=1.72, 95%CI:1.41 - 2.11), eating speed <10min/meal(OR=1.29, 95%CI:1.05 - 1.57), sedentary behavior >2h/d(OR=1.51, 95%CI:1.24 - 1.85), insufficient exercise endurance(OR=1.56, 95%CI:1.12 - 2.19), and screen time>1h/d(OR=1.42, 95%CI:1.16 - 1.75). 【Conclusions】 The detection rates of overweight and obesity among preschool children in Suzhou are relatively high, and the detection rate and severity of obesity increase with age. In addition to genetic factors, preschool obesity are also associated with pregnancy and birth history, as well as unhealthy lifestyle after birth.