This study, viewing from the lens of population security and drawing upon the seventh national census data, utilizes the DCMD three-parameter model life table and the cohort element method to forecast and project China's death population, the population of childbearing women age in their prime years and the working-age population, so as to comprehensively study the trend of China's negative population growth and its characteristics in the future. Findings suggest that over the next 30 years, on the one hand, with the aging of the two post-establishment birth booms in China, the death rate continues to rise; on the other hand, as the birth cohorts from 1984-1990 gradually move out of their prime childbearing years, and with fewer women entering this phase, there is a contraction in the number of women in their prime childbearing years, leading to an aging age structure and a continuous decline in birth. The combined effects of these two factors will result in a continuous decrease in China's population. In response, it's vital to seize the window of opportunity from 2031-2040 when the number of women in their prime childbearing years increases, actively promote support policies to stimulate fertility potential; tap into the significant "demographic dividend" of younger aging during the early stages of negative population growth and swiftly introduce a progressive policy of delayed retirement.