The theoretical studies of population security have been on the decline in recent years. This paper conducts a literary review of the birth, development and decline of the theory, examines the causes of the decline and proposes a new perspective – population securitization -- to revive, enrich and revitalize the theory. The theory of population security was born in China and it is a branch of the non-traditional security-management theory put forward by Zhang Weiqing during the period of SARS. After the birth of the theory, there was a heated discussion in the academic circle, and “population security” was a high-frequency keyword both in policy reports and in academic research papers. The amount of literature reached its peak in 2005 in CNKI’s database, covering the concept, application and significance of population security. However, after SARS died down, academic research went into decline as well, as is evident in the amount of literature in CNKI’s database after 2006. This is not because China had fewer population problems, but because scholars were turning to other concepts instead. On one hand, population security is an abstract concept which covers all the threats to population and is therefore not an ideal concept for empirical research which is typically multi-topical and specialized. On the other hand, even though population security highlights threat, it can be easily replaced by other terms. However, during the formation of the theory, the process of speech acts constituting threat, i.e., the process of securitization, was neglected. This is a concept which cannot be replaced by other concepts. The problem of population security can thus be understood as a “securitized” population problem, while the population problem which has not been securitized is a silent one. The danger of the silent security problem lies in people’s neglect of population-related threats, and the significance of securitization is to raise people’s awareness of and alertness to such threats and to take due action. There are two approaches to securitization: politicalization and socialization. The former constructs threat by policy and law, while the latter does this by constructing a civil society. The advantage of the former is the authority of the government, while that of the latter is its flexibility. These two approaches can be applied simultaneously so that their different roles can be exerted.