In a statement read on the evening news, the Chinese government said it would adhere to the principle of limiting family size while promoting the "long-term balanced development of the population of China."
The Chinese government also pledged to improve its human rights record by abolishing the much-criticized "reeducation through labor" program, which allows people to be sent to labor camps for up to four years without trial.
The statement also promised to reduce land confiscations -- a major grievance in the Chinese countryside -- and to reduce the number of crimes eligible for the death penalty, something that has been an ongoing process.
However, it is the change in the one-child policy that is likely to have the most immediate effect on Chinese families. Demographers have estimated that about 10 million couples will be allowed to have a second child as a result of the change.
The law currently allows couples to have a second child only if each parent is an only child.
Since the law was first adopted in 1980, Communist Party officials have tweaked the rules repeatedly, allowing various exceptions for minorities and rural families, but there have been few major amendments of this kind.
China’s National Health and Family Planning Commission says the law has kept the country’s population of 1.3 billion in check, preventing 400 million births.
Demographers say that the effect has been exaggerated and that the law instead has led to a gender imbalance, with more boys than girls born, and that it could impair China’s growth by creating an aging population with too few workers.