Phan-Gillis was sentenced to three and a half years in prison by a court in Nanning, but it is unclear if she will have to serve the time.
She was arrested in March 2015 while travelling with a business delegation from Texas through mainland China.
She has already spent more than two years in detention and her family has consistently maintained her innocence.
Phan-Gillis, who has Chinese origins but was born in Vietnam, was accused of espionage and stealing state secrets, according to the UN Working Group on Arbitrary Detention.
