The average annual growth rate was 0.53% over the past 10 years, down from a rate of 0.57% between 2000 and 2010 - bringing the population to 1.41bn.
The results add pressure on Beijing to boost measures for couples to have more babies and avert a population decline.
The results were announced in a once-a-decade census, which was originally expected to be released in April.
The census was conducted in late 2020 where some seven million census takers had gone door-to-door to collect information from Chinese households.
Given the sheer number of people surveyed, it is considered the most comprehensive resource on China's population, which is important for future planning.
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