Abstract: The original data of age and sex-specific constitution of population from the four censuses of China after smoothed by moving mean are ultilized to analyse the change of two-sex age-specific survival rates and their difference during intercensal periods and age- specific sex ratios of each census at older ages. The results show that the trend of rapid decline of two-sex survival rate with age levels off and even rises at older ages over 90. At old ages male age-specific survival rate is lower than that of female, but at the advanced ages over 90 this difference lessens and then turns to enlarge reversely. The results imply that although male average life expectancy is shorter than that of female, genetic life-span of male is not shorter than that of female.

Key words: Older ages, Age-specific survival rate, Sex ratio , Two-sex difference