It stood at 10.94 per thousand in 2018, compared to 12.43 per thousand in 2017, according to data released by the country's statistics bureau.
It has never been lower in the history of the People's Republic of China, which was founded in 1949.
The new figures mean that 2 million fewer babies were born in China in 2018.
Figures also show that the rate of natural increase in population, deducting the number of deaths, has also slowed.
It is now at its lowest level since the aftermath of a famine in the early 1960s.
China relaxed its notorious one child policy in 2016 by allowing urban couples to have two children, but the new rules have done little to encourage more births.
The policy change was spurred by fears about the country's increasingly ageing population.
China's statistics bureau did not suggest a reason for the rate's fall, but in 2018 economic growth in the country fell to its lowest in nearly 30 years.
Many couples are reluctant to have children due to high property prices and soaring healthcare and education costs.
In January, a government-affiliated think tank warned that the population in the world’s second-biggest economy could start to shrink as soon as 2027.
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