The number of unmarried Chinese men between 35 and 59 will reach 15 million in 2020 and 30 million in 2050, Wang Guangzhou, a researcher at the Chinese Academy of Social Sciences said.
Poorly educated lower class men are far more likely to end up single, he told state-run People's Daily.
This is because males who only have a primary education or below increased to 15 percent in 2010.
Yuan Xin, a professor at Nankai University and expert on family planning policy, told state run Global Times that the number will likely exceed 30 million in 2050, as gender bias in favour of males at birth is still high in China.
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Two males for every 100 females in China in 2004, while the standard ratio set by the UN is between 103 and 107 males for every 100 females.
In 2015, the nationwide average was 113. Five males against 100 females, the seventh decrease since 2009.
Zhai Zhenwu, a sociologist at the Renmin University of China, said the continued imbalance was caused by the development of ultrasound technology in the 1980's, which aided the traditional family preferences for a son, the People's Daily report said.
"The family planning policy which also promoted late birth had the negative effect on increasing the desire for people to select the sex of their child.
China bans any testing for gender or selective abortion over gender preference.
Data released by the National Bureau of Statistics on January 20 shows that China's male population reached more than 708 million at the end of 2016, while the number of females was more than 675 million.
China's sixth national population census in 2010 showed that unmarried Chinese women above 30 years old accounted for 2.47 per cent of the female population - almost two times higher than the figure reported in the 2,000 census.
"Besides the marriage issue, a high single male population might also cause many other social problems such as sexual violence, women and child trafficking, not to mention the pension burden they will bring about when they get old," Yuan said.
The National Health and Family Planning Commission said early this month that China would reduce its sex ratio at birth to 112 boys for every 100 girls by 20.
Already the widening sex ratio prompting rural Chinese men to marry women from neighbouring east Asian countries like Vietnam.