Abstract:On March 11, 2011, the Fukushima Daiichi Nuclear Power Plant was severely damaged by the massive 9.0 earthquakes and tsunami that struck off the northeast coast of the Island of Honshu. The damage to the nuclear facility has resulted in substantial environmental releases of radioactive materials into atmosphere. As a consequence, on March 26, the radioactive material I 131 from Fukushima Daiichi nuclear accident (FDNA) was monitored in China’s Heilongjiang air sampling for the first time. The monitoring of FDNA in China lasted for nearly a month, till April 22, the radioactive substances monitored in China mainland, which are I 131, Cs 137 and Cs 134, were close to basic values. Based on these monitoring data and HYSPLIT’s forward and backward trajectory modeling, this paper estimates the impacts of Fukushima Daiichi accident on China’s radioactivity levels. During the monitoring period, the maximum concentration of I 131 which is located in Jilin Province, is 8.01 mBq·m 3 and occurs in April 7. This value is closely related to the prevailing eastern winds during this period. Meanwhile, relatively high I 131 concentration is monitored in North China, the Northeast and Northwest of China. For Cs 137 and Cs 134, the maximum values both are found in the Xinjiang Region, being 1.55 and 1.42 mBq·m-3, respectively around April 4 and 9. At the same time, the trend of national averaged concentration shows two peaks around. Northwest and North China are found to have higher concentration of Cs 137 and Cs 134. Additionally, the ratios of Cs 137/I 131 and Cs 134/Cs 137 are analyzed and compared with the measurement results by other countries. The Cs 137/I 131 activity ratios (0.04-0.9) are observed to increase with time as expected from radioactive decay, and Cs 134/Cs 137 activity ratio is measured near the line 1.0.