This paper discussed the different methods of calculating the age-specific mortality rate according to the different nation's population size,based on the 2000 census,which can provide the indicators of mortality at the end of 1990s.The results shows,that the mortality of all nations are decreasing comparing to the level 10 years ago,and there is some phenomenon that can't be ignored.For example,the number of nations is increasing,whose female infant mortality is higher than the male.Some nations remain the high mortality level.Besides that,this paper discussed the random error of mortality while the change of mortality was biased.