The man is believed to have passed on information about Uighurs living in the southern city of Munich, home to the world's biggest Uighur diaspora, from at least April 2008 until October 2009, federal prosecutors said.
"Until October 2009 he regularly gave information about members and organisations either by phone or in meetings with his intelligence contacts," prosecutors claimed.
The man, who has not been named, was charged on February 7.
China's roughly eight million Turkic-speaking Uighurs have long complained of religious, political and cultural oppression by Chinese authorities – which China denies – and tensions have simmered in the Xinjiang region for years.
China says it faces a serious terrorist threat from Muslim separatists in Xinjiang, but rights groups have accused Beijing of exaggerating the threat in order to justify tight controls in the vast region.
Fierce clashes in Xinjiang in July 2009 between the local Muslim Uighur community and China's majority Han ethnic group left nearly 200 dead and more than 1,700 injured, according to an official toll.
Xinjiang authorities cut off the internet during the unrest and for 10 months afterwards, alleging it was being used by instigators to foment violence. Press freedom groups say access remains severely restricted.