A new policy guideline eases the law on most illegally adopted children in China.
The legal rights of these children are currently not guaranteed such as permanent residence of a city, schooling and inheritance.
The guideline was jointly issued by five ministries on Sept 5, but made public on Monday.
It allows people to register their illegally adopted children without fear of punishment.
Ji Gang, director of the China Center of Adoption Affairs, said the number of illegal adoptions has been increasing rapidly in recent years.
"In less developed areas, the number of unregistered adoptions can be two or three times more than registered ones," he said.
"In big cities where people have a better knowledge of the law, the number of unregistered adoptions is fewer."
Shanghai, for example, between 1992 and 2000, had more than 7,000 registered adoptions and about 4,000 unregistered ones.
Ji said China has more than 20,000 registered adoptions every year.
To adopt a child legally in China, a person must be more than 30 years old, healthy, childless and with a good and steady income.
Those seeking registration under the new guideline will be exempt from these requirements except in the case where a single male parent is not more than 40 years older than the girl he has adopted.
If this is not the case, the man will be persuaded to surrender the child to a children's welfare institute.
The guideline also requires anyone who finds abandoned babies to hand them over to police in the first instance.
If the police fail to find their biological parents, the children will be handed over to local children's welfare institutions.
If people who find such babies meet the necessary requirements and want to adopt them, they will be given first priority.
"It means you can not take an abandoned baby home and then apply for adoption. They must be handed over to the authorities first," Ji said.
He said the guideline will help in the fight against trafficking of infants and children.