Through illustrating the implication of aging population and investigating the pension security system of Xi'an, this paper analyzes the problems existing in the current system: first, the level of the pension security of the social vulnerable groups is very low; second, the loads imposed into the individuals and families are heavy; third, the responsibility of the government in the pension security is lacked to some extent; and the last, the staff for serving the pension security is less and should be supplemented urgently.