Hong Li said her husband, Hu Zhicheng, arrived at Los Angeles International Airport from China on Monday night.
"We're grateful, we're very, very grateful for everybody's help and we're really happy to have him back home," she said of herself and the couple's two children.
She told The Associated Press in a brief phone interview Tuesday night that her husband was asleep and still jet lagged and did not want to talk about his ordeal or his return home.
Hu was released just ahead of a summit between President Barack Obama and Chinese leader Xi Jinping, but Li said she didn't know if that played any part in her husband's return.
China's government has in the past released prisoners or resolved cases like Hu's to improve relations with the U.S. ahead of major meetings.
Li said she first learned he was coming home in a call Monday from a relative in China, who told her he was on a plane to the United States.
"We have seen the press reports, and are pleased that Dr. Hu is home with his family," the State Department said in a statement.
A spokesman at the U.S. Embassy in China had no immediate comment.
An internationally recognized expert in the development of catalytic converters that are used to limit pollution in automobiles, Hu holds a doctorate in engineering and more than 50 patents. He has performed research at the Massachusetts Institute of Technology and worked for international companies.
He returned to China in 2004 after years in the U.S., hoping to get in on the ground floor building cleaner-running automobiles just as smog-choked China's economy was booming.
Hu became chief scientist and president of a company trying to build top-grade catalytic converters and was honoured by the province of Jiangsu as one of its leading innovators. Li, meanwhile, started her own business supplying materials to the company that employed her husband. She also holds a doctorate in engineering.
Eventually, a competitor accused Hu of stealing information and providing it to his wife's company. When Li and the couple's children returned to the U.S. for a summer visit in 2008, he was nervous enough to warn them not to come back to China. Shortly before Thanksgiving that year, he was arrested.
Hu was jailed for 17 months while police investigated the case. He was eventually cleared of any wrongdoing and released, but authorities refused to let him leave China after his business rival filed a lawsuit seeking financial damages.
Li said Tuesday she didn't know if that case has been resolved.
After his release from jail, Hu moved to Shanghai and worked for the company that employed him. He was allowed to travel freely within the country, but he could not leave. Asked Tuesday if he would consider returning at any point, Li laughed.
"No, I don't think so. I doubt it," she said.
The couple was born in China and became U.S. citizens several years ago. Both of their children were born in the U.S.
Their daughter, Victoria Hu, visited her father in Shanghai in 2010 and since then has kept up a relentless campaign from the United States seeking his release.
She posted a petition to Change.org that collected more than 60,000 signatures and started a Facebook page called "Help Victoria's Father Dr. Zhicheng Hu Come Home."
Her mother, meanwhile, contacted the State Department and other officials for years.
All of those efforts had seemed to lead nowhere until Monday.
Associated Press writer Charles Hutzler in Beijing contributed to this report.