In a dramatic confession before a federal court in Virginia, Gao Zhan pleaded guilty to exporting 80 micro-processors to China without required authorisation from the US Department of Commerce.
The hi-tech equipment that she sent could well have been used in weapons systems.
Gao had been sentenced to 10 years in jail in China in 2001 on charges of spying for Taiwan.
The conviction catapulted Gao, an academic researcher and US permanent resident, to the status of a celebrated human-rights icon and Washington exerted immense diplomatic pressure to secure her release.
She was released on 26 July 2001, just days before a visit to Beijing by US Secretary of State Colin Powell, after a five-months stay in jail.
In her plea bargain deal on Wednesday, Gao also confessed to filing a false joint tax return with her husband Xue Donghua, which did not include most of the proceeds of the sales worth $1.5 million.
Sentencing has been set for 5 March.
The maximum penalty for her offences is 13 years in jail and a half a million dollars in fines.
According to court documents, Gao sent the micro-processors to Nanjing Research Institute of Electronics Technology, which makes radar systems for the Chinese military.
For national security reasons, such components require a Commerce Department license before they can be exported to China.
Gao's lawyers argued the case resulted from a misunderstanding, saying she believed that the company was a civilian one and that the parts involved all had civilian and commercial users.