Reform of old-age-insurance system for public institutions is currently concerned by society. The article splits the institutions old-age-insurance under single pillar into three pillars of national annuity, and basic old-age insurance and the career annuity, according to the design concept of """"three pillars"""" our country has advocated. And based on the principles of "adjustment structure, and maintained original security level", the paper measures the security level of each pillar using statistics data, and verifies the payment ability of our country, and public institutions and individuals.