South Korean women is predicted to break the 90-year barrier by 2030. Does life disparity by gender tell same story with such gains in life expectancy? To date, almost all of the research on mortality variation were from Western countries, but there is a dearth of such studies from South Korea. We fill this important gap in understanding of mortality transition in terms of life expectancy change and associated trajectories of age-at-death variation through life disparity by gender in South Korea. Using complete life tables of South Korea from 1970-2015, we analyse the change in sex differentials in life disparity and life expectancy over time and decompose these sex differentials by age and cause of death. The results show that the sex differentials in life disparity has widened in 1970s and 80s and remained stagnant thereafter until 2015 along with life expectancy. Females enjoy higher life expectancy and have lower life disparity in 2015 mainly due to lower mortality of middle age (40-60 years) and old age (60-80 years). However, higher life expectancy for females in 1970 was not translated into lower life disparity due to higher mortality of adult age (25-30 years) and old age (60+).