The man, named as Chen Wei from the eastern coastal province of Zhejiang, was recruited while working overseas, state television said late on Wednesday, in its second report this week on people jailed for security-related crimes.
Chen's recruiter, Ji Tian, whose nationality was not specified, roped him in by initially feigning an interest in Christianity and saying he also wanted to learn Chinese, the report said.
Ji used their growing friendship to ask Chen to take pictures of harbours in Zhejiang - which lies close to the disputed and uninhabited islands, called the Diaoyu in China and Senkaku in Japan.
Chen was caught in December 2013 after taking pictures of a military base and sentenced to seven years in jail, state television said.
The report did not say when he was sentenced.