To analyze the characteristics and trends of body mass index (BMI) among young men in China using data from a series of national surveys conducted between 1955 and 2012, and to provide evidence for policy making and disease control and prevention.BMI-related data were collected by routine medical examination from young men, most aged 18 to 20 years, in 4 national surveys (1955, 1974, 2001, and 2012) using a stratified cluster sampling method in 31 provinces, autonomous regions, and municipalities in China. The characteristics and trends of BMI during this period were analyzed by region, year, age, and economic level.Totals of 266,791, 118,092, 69,776, and 57,969 participants were included in the 4 national surveys, respectively. Between 1955 and 2012, height, weight, and BMI showed increasing trends in men aged 18 to 20 years at the national level and in each of the 6 areas of China. BMI also differed among geographical regions. Data from the 2012 national survey showed that age (17-22 years) was correlated positively with the prevalence of overweight and negatively with the prevalence of underweight (both P < 0.05). Gross domestic product was correlated negatively with the prevalence of underweight (r = -0.25) and positively with the prevalence of overweight and obesity (r = 0.45 and 0.240, respectively; all P < 0.001).BMI increased with economic development among young men from 1955 to 2012, with distinct variation among geographic areas in China. Although underweight remains prevalent in young men, especially in urban and northern regions, overweight and obesity are increasingly prevalent and warrant public health attention.