Various experiments to measure radon migration coefficients indicated that the migration of radon and its daughters is directional.The horizontal diffusion data of radon in the air has been measured and studied in laboratory conditions using the accumulative radon-measurement method in a static state with high sensitivity.The mathematical calculation to obtain horizontal diffusion coefficients of radon under the condition of different temperature is done by fitting a difference equation to the measured radon diffusion data.A linear positive correlation coefficient of 0.92 between horizontal diffusion coefficient of radon and diffusion temperature

was obtained.The horizontal diffusion coefficient of radon is 0.049 cm2·s–1 at constant temperature of 30°C.To obtain the typical radon diffusion coefficient of 0.1 cm2·s–1

the diffusion condition of above 40°C can be deduced.