A lieutenant commander assigned to the Defense Security Command faces charges that he handed over classified information to a suspected Chinese agent while studying in China from 2009 to 2012.
He allegedly passed military materials to a university student in return for money.
South Korean authorities suspect the Chinese student was a spy.
In June, two officials from the Defense Security Command were sentenced to six years and four years in prison respectively for passing classified information to arms dealers.
The incidents have dealt a blow to the Defense Security Command, whose tasks include the prevention of espionage and the establishment of discipline within the military.