To analysis the development status of height and mass with Han, Mongolian students in Inner Mongolia and Japanese students aged 7-18 in 2014, and explore national difference of the maximum growth age in height and mass. The data of Han and Mongolian students were from “2014 survey on the physical fitness and health of students in Inner Mongolia autonomous region”; Data of Japanese students were obtained from “statistical information of the Heisei 26 annual sports survey” of Ministry of Education, Culture, Sports, Science and Technology-Japan. The national differences of the development status of height and mass, maximum growth age in height and mass(MIA-H, MIA-W) among Han, Mongolian and Japanese students were compared. The Results showed that height of both Han male and female were taller than Mongolian and Japanese at aged 7-18, 1.98 cm and 1.54 cm higher than Mongolian, and 2.59 cm and 2.91 cm higher than Japanese on average respectively(P<0.05). The height of Mongolian male and female were 0.61 cm and 1.37 cm taller than Japanese (P<0.05).The mass of Han male was 1.97 kg Heavier than that of Mongolian and 4.01 kg Heavier than that of Japanese on average(P<0.05). The mass of Han female was similar to Mongolian, and 2.59 kg and 2.67 kg heavier than Japanese on average respectively(P<0.05). Han boys has the earliest maximum growth age in height(HIA-H) at 10.66 years, which is followed by Japanese in 11.56 years and Mongolian in 12.39 years. The HIA-H of Japanese female was 9.73 years; Han and Mongolian female were 10.41 years and 10.10 years respectively. The maximum growth age of mass(MIA-W) among Han Mongolian and Japanese male were 12.52 years,12.62 years and 11.45 years; MIA-W in female was 10.59 years, 10.34 years and 10.14 years respectively. In 2014, the development levels of height and mass of Han and Mongolian students aged 7-18 in Inner Mongolia were higher than Japanese students of the same age. HIA-H of Han male was 1.73 years earlier than Mongolian and 0.9 years earlier than Japanese respectively, and HIA-W of Han and Mongolian male were 1.17 years and 1.07 years later than Japanese. HIA-H of Japanese female was 0.68 and 0.37 years earlier than Han and Mongolian.