Exposure to mercury was assessed in 125 Korean (Gwangju and Busan) and 373 Chinese primary school students (Xinguang village, Goumen town) using hair mercury analysis from November 2006 to September 2007. The geometric mean concentration of mercury was higher among Korean children with recording 0.73 ${mu}g$/g, compared to Chinese children of 0.12 ${mu}g$/g, which indicated statistically difference (P<0.01). The mean concentration of Korean children living near incineration facilities was higher by recording 0.76 ${mu}g$/g while the average concentration of their counterpart in Korea reached 0.69 ${mu}g$/g. In case of Chinese children, those who are living near power plants showed higher level with posting 0.16 ${mu}g$/g while the others recorded 0.10 ${mu}g$/g (P<0.01). Intake of fish was found to be related to hair mercury level. In case of Korean children, those with high fish intake recorded 0.79 ${mu}g$/g in terms of the geometric mean concentration while the others with low fish intake posted 0.61 ${mu}g$/g. Among Chinese children, those who often eat fish recorded 0.13 ${mu}g$/g compared to the others with low fish intake of 0.11 ${mu}g$/g. On the other hand, amalgam dental fillings have limited influence on mean hair mercury level. As for vaccination, within a month of vaccination, the geometric mean concentration of Korean children reached 0.76 ${mu}g$/g, and in case of 15 days after injection, the level was 1.20 ${mu}g$/g. In China, the level of children at one month after receiving injection stood at 0.15 ${mu}g$/g while the level within 15 days was 0.13 ${mu}g$/g. Multiple regression analysis showed that BMI, passive smoking, and fish consumption are closely related to hair mercury level among the Korean subjects. In China, hair mercury level was affected by age, location, passive smoking, fish consumption, and vaccination. Explanatory power was 21.6% with $R^2$=0.216.