According to the three levels of population aging, this paper puts forward the design scheme of three-dimensional old-age security structure, and explores the linkage development law between the promotion of population aging level and the optimization of three-dimensional old-age security structure. The research puts forward: (1) Under the condition of prolonging the life span of the elderly population, according to the life-cycle-age-coefficient, the age coefficient of the elderly population is divided into three levels: initial-aging-coefficient, high-aging-coefficient and super-aging-coefficient. (2) According to the three ways of income redistribution of old-age security, the old-age security system is divided into three-dimensional structure: one dimension is the intergenerational transfer of pay-as-you-go horizontal income redistribution of old-age security; the second dimension is the vertical income redistribution of individual life cycle old-age security; The third dimension is the redistribution of comprehensive income of social old-age security. (3) At the level of early aging, one-dimensional old-age security can achieve an appropriate level; at the high level of aging, one-dimensional and two-dimensional old-age security can reach an appropriate level; at the super aging level, one-dimensional plus two-dimensional plus three-dimensional old-age security can reach an appropriate level. The overall linkage of the three-dimensional old-age security structure is conducive to actively deal with the risk of imbalance between supply and demand of old-age security caused by the extension of the life span of the elderly population. (4) The optimization of three-dimensional old-age security structure has the coordinated development of social and economic relations, such as intergenerational old-age ethics and old-age cost return, personal old-age savings and advanced consumption in youth, public capital and public old-age responsibility, social transfer payment and old-age replacement rate surplus. On this basis, it puts forward policy suggestions for the construction of old-age security system.