Abstract: According to the distribution of cosmic ray ionization with altitude andlatitude as well as the census information in all of our country (the endof the year 1986), the population-weighted mean annual effective dose equivalentreceived by the population living at mainland areas in China is estimated to beabout 278 μSv, in which the ionizing component and the neutron component are252 μSv and 26 μSv, respectively.