The United States and international human rights groups have called for the release of Tal al-Mallohi who has been held since December 2009. Her blog, known for poetry and social commentary, focuses mostly on the suffering of Palestinians. It was not clear whether al-Mallohi's arrest was connected to the blog.
Syria's Higher State Security Court issued the sentence at the end of a trial behind closed doors Monday, an official close to the court told The Associated Press.
The court convicted al-Mallohi of "contacting a foreign country," the official said. "She has leaked information that should be kept secret," the official said on condition of anonymity because of the sensitivity of the case.
The official did not identify the country she was accused of spying for or give any other details. He said al-Mallohi "deserved 15 years in prison but her sentence was commuted considering her age."
A Syrian official in October said her alleged spying had led to an attack against a Syrian army officer by agents of the foreign country she was spying for. He did not elaborate.
The U.S. on Saturday condemned Syria for the secret trial and appealed for al-Mallohi's immediate release.
State Department spokesman P.J. Crowley sharply criticized Syria's handling of the case. He rejected what he called "baseless allegations of American connections that have resulted in a spurious accusation of espionage."
Crowley called on Syria's government to release all prisoners of conscience and allow citizens to exercise their rights without fear of retribution.
Syria's private Al-Watan newspaper alleged in October that al-Mallohi had spied for the U.S. embassy in Cairo, triggering a November 2009 assassination attempt against a Syrian security officer on a Cairo street. The attack left the officer disabled.
There was no official Syrian comment on the report.
Syrian authorities routinely crack down on political activists, putting them on trial on suspicion of engaging in anti-government activities.
The New York-based Human Rights Watch last year quoted al-Mallohi's parents as saying she does not belong to any political group.
Some Syrian activists have expressed concern that security services may have detained her over a poem she wrote criticizing certain restrictions on freedom of expression in Syria.