Abstract: According to the demographic transition theory,negative population growth in post-demographic transition period is a special population reproduction pattern under the effect of ultra-low fertility.It refers to the phenomenon of rapid change that the number of deaths exceeds the number of births without migration,and the total population and growth rate,age structure and distribution structure.The forecast data in 2020 of the University of Washington outlines the basic trend of the global negative population growth in this century for the first time.Compared these data with the UN forecast in 2019,this paper finds that the mechanism of the global negative population growth in this century lies in the expectation about low fertility rate.Looking forward to the trend of negative population growth in the world,it is found that the accelerated aging of population age structure,the imbalance of regional and national population development,and the differentiated relationship between population and economic development are accompanied by negative population growth.Negative population growth is accompanied with the population aging by reducing labor resources,squeezing the space for technological progress,and increasing social security pressure.Negative population growth is also associated with the risk of low fertility traps in the post-demographic transition stage,interacted with resources and environment through the overall and individual perspectives.It is urgent to relieve the aging society problems,implement different family planning policies and promote sustainable development actively on the basis of adapting to the law of negative population growth.

Key words: negative population growth, demographic transition, population aging, aging society, sustainable development