Liu Sixing, who formerly worked in US company L-3 Communications, was accused of taking information on US missile, rocket and drone technology to China.
He was convicted of exporting military information, possessing stolen trade secrets, and lying to the authorities.
Liu says he did not break the law, or intend to pass secrets to China.
Liu Sixing, who was also known as Steve Liu, worked in L-3 Communications' space and navigation unit in New Jersey from 2009-2010 as a senior engineer.
Prosecutors say he stole thousands of computer files in 2010, and took them to China on his personal computer, where he gave presentations about the technology he was working on to universities and conferences linked to the Chinese government.
Prosecutors say he transported the files, which included information on the performance and design of guidance systems for missiles, rockets and unmanned drones, in the hope that it would help him gain future employment in China.
Federal agents say they discovered the computer when Liu returned to Newark Liberty International Airport in November 2010. Liu was convicted in September 2012.
Technical military data covered by US export regulations cannot be taken out of the country without a license.
"Instead of the accolades he sought from China, Sixing Liu today received the appropriate reward for his threat to our national security: 70 months in prison," prosecutor Paul Fishman said.
Liu's lawyer, James Tunick, said that Liu had made "a terrible mistake" by having the files on his computer and taking them to China, but that "it didn't rise to the level of a criminal act."
"He never intended to harm anyone," he said.