Objective To understand the prevalence of obesity among preschool children in urban area of Qingdao and the trends in recent years,so as to provide theoretical evidence for effective control and intervention of obesity. Methods A convenience sampling method was used to select 13 medium-sized kindergartens in Qingdao urban area from April to June in 2018.The height,weight,waist circumference and hip circumference of all children were measured.And the data were compared with those in 2006,in order to study the trend of obesity in preschool children for 12 years. Results The detection rate of obesity among children aged 3 to 6 years in this survey was 7.51%,which was significantly lower than that in 2006(9.52%,χ²=11.218,P=0.001),with annual decline of 16.75% on average.Also,the detection rate of obesity in boys(10.02%) was significantly higher than that in girls(4.80%,χ²=42.11,P<0.001).Likewise,the detection rate of overweight in children aged 3 to 6 years in 2018 was 15.85%,which was significantly lower than that in 2006 (18.12%,χ²=7.892,P<0.05).The BMI,waist-to-hip ratio and waist-to-height ratio of obese children were significantly higher than those of normal weight children (P<0.001). Conclusions The obesity in preschool children in Qingdao city has been effectively controlled over the past 12 years.Although the detection rate of overweight in children has decreased,it is still much higher than the detection rate of obesity.So it is suggested that preschool overweight children should be regarded as the key population to prevent and control the overweight children,in order to avoid its transformation into obesity in school age and adulthood.