Beginning in 2016, all couples in China were allowed to have two children without any restrictions. This paper provides population and economic projections under five shared socioeconomic pathways (SSPs) and three fertility policies. By replacing the one‐child policy with the two‐child policy, the population is predicted to continue growing until 2025–2035, with a peak of approximately 1.39–1.42 billion, and then to decline under four SSPs, with the exception of the fragmented world SSP3. As a result, the two‐child policy will lead to mitigation of the pressure from labor shortages and aging problems to a certain extent. In addition, an increase in working‐age people with higher education level relative to projections based on the one‐child policy will lead to an increase in gross domestic product by approximately 38.1–43.9% in the late 21st century. However, labor shortages and aging problems are inevitable, and the proportion of elderly in China will be greater than 14% and 21% by approximately 2025 and 2035, respectively. Full liberalization of fertility is expected to reduce the share of elderly people by 0.7–1.0% and to lead to an increase in gross domestic product by 5.3–6.7% relative to the two‐child policy in the late 21st century. The full liberalization of fertility policies is recommended, supplemented by increases in pension and child‐rearing funds, improvement in the quality of health services for females and children, and extension of compulsory education to meet the needs of an aged society. Plain Language Summary The one‐child policy in China has been replaced by the two‐child policy since 2016. What might the population and economy change if the one‐child policy is continued in the 21st century? What can China benefit from the fertility policy changes? Is it necessary to allow people to choose their family size in China? We conducted multipopulation policies and multisocioeconomic development pathways combined analysis to explore the effects of fertility policy changes on population and economy in China. We found that population size by the late 21st century might be 28% less than that in 2010 at the one‐child policy, and share of elderly (aged 65+) might be 49%. The implementation of the two‐child policy can mitigate the labor shortages and aging problems to a certain extent, and the increased working‐age population with higher education level can lead to a 38.1–43.9% increase in gross domestic product in the late 21st century. A further 0.7–1.0% reduction in elderly share of the total population and 5.3–6.7% increase in gross domestic product is projected in the late 21st century at the “full relaxation” policy. We believe that introduction of effects from fertility policy changes on socioeconomy can deliver useful information to decision makers. Key Points The integrated effects of population policies and socioeconomic pathways on the population structure and economy are explored The population bust in China caused by the one‐child policy will be relieved after the two‐child policy, as indicated by all the SSPs Full relaxation of fertility control is recommended with the simultaneous implementation of other social policies (e.g., pension funds)