This study aims at investigating parenthood attitude toward adult children’s second birth under the "two-child"policy based on the Beijing Empty Nest Family Survey in 2015.The survey shows that the elderly present high awareness rate of the "two-child"policy; old parents who support,oppose to,or hold the idea of non-interference to their married children’s second birth account for one third respectively; almost 70% of the elderly would support their adult children’s second birth through economic assistance or child care; utilitarian purposes,such as old age care,are no longer primary reasons for second birth; economic cost,concern about mothers’ or baby’s health and lack of child care resources become the top three factors preventing second birth.Having a good relationship with adult children,good health condition and being currently married have a significantly positive effect on parenthood supportive attitudes toward adult children’s second birth; open-minded idea on endowment,education and duration of the empty nest period significantly reduce the probability of the elderly to support children’s second birth; and no significant effect is found with gender,age,economic condition and preferable place for old age life.