准确预测2015、2020年北京市常住人口结构，分析不同生育政策对北京人口结构的影响。论文采用考虑迁入人口的人口-发展-环境模型（PDE），以第六次北京人口普查数据为基础，用时间序列做死亡率参数估计，预测北京市在三种不同生育政策下2020年的人口结构。结果显示：北京市2015年的人口总量约为2156.7万，北京处于低生育率、人口老龄化状态。在中方案（即实施单独二胎政策且按意愿生育）假定条件下，北京市2020年人口总量约2338.9万人，人口结构逐渐年轻化，老龄化趋势得到明显改善；在低方案（即保持计划生育政策不变）假定条件下，北京市2020年人口总量约2316.7万，儿童少年比例小，老龄化问题突出；在高方案（即实施完全二胎政策）假定条件下，北京市2020年人口总量约2361.9万，人口结构更加年轻化，但将带来人口的持续增长,十年内将多增100万人口左右。

Accurate population structure prediction of Beijing in 2015, 2020 can provide an important basis for the development of relevant policies. Based on Beijing’ sixth population census data, this paper estimates mortality parameters by time series, and forecasts the population structure in 2020 under three scenarios of low, medium, high birth rates set by the separate two-child policy through the population-development-environment model(PDE). Result shows that: the total population in Beijing is 21,567,000 in 2015 and Beijing is in the low fertility, population aging state; Medium birth rate that is implemented according to the separate two-child policy and the wishes of fertility,has23,389,000total population in 2020 in Beijing. Its population structure becomes gradually younger, and demographic aging trend has been significantly improved; one-child policy is not changed in low birth rate. The total population in 2020 is 23,167,000 in Beijing, and it has a small proportion of children and adolescents, highlighting the problem of aging; High birth rate that is parents who meet the full two-child policy all have second child, has 23,619,000 total population in 2020 in Beijing. Though its population structure is younger, it will bring rapid population growth, and about 1,000,000 people will be increased next 10 years.