In some provinces, 130 boys are born for each 100 girls
More than 24 million Chinese men of marrying age could find themselves without spouses by 2020, says the Chinese Academy of Social Sciences.
The gender imbalance among newborns is the most serious demographic problem for the country's population of 1.3 billion, says the academy.
It cites sex-specific abortions as a major factor, due to China's traditional bias towards male children.
The academy says gender selection abortions are "extremely common".
This is especially true in rural areas, and ultra-sound scans, first introduced in the late 1980s, have increased the practice.
The latest figures show that for every 100 girls born in China, 119 boys are born, the academy says in a new book.
Researcher Wang Guangzhou, quoted by the Global Times newspaper, said the implications were that men in poorer parts of China may remain single throughout their life.
CHINA'S GENDER IMBALANCE
119 boys born per 100 girls. Rises to 130 boys per 100 girls in some rural areas
Total population 1.3 billion
Expected peak 1.6 billion in 2050
One child policy written into constitution in 1978
Many rural couples allowed second child if first is a girl
"The chance of getting married will be rare if a man is more than 40-years-old in the countryside. They will be more dependent on social security as they age and have fewer household resources to rely on," he said.
In some provinces, 130 boys are born for each 100 girls, the book says.
Experts at the academy also predict the gender imbalance will lead to more inter-generational marriages, where a wife is older than her husband.
A reluctance among young urban Chinese to have a first or second child is exacerbating the problem.
Academy sociologist Yan Hua said: "People's minds have changed a lot during the last 20 years.
"Young couples either don't want to have a second child, or would prefer to live a DINK (Double Income No Kid) life."
The growing imbalance means that forced prostitution and human trafficking has become "rampant" in some parts of the country, according to the researchers.
While analysts admit there is definitely a pronounced gender imbalance in China, they also say that exact information is difficult to obtain because some families are thought to avoid registering female babies in order to make it easier for them to have a second child.