By ANDREW JACOBS

BEIJING — In a case that has prompted a number of appeals from the White House, a Chinese court on Friday upheld the conviction of an American oil geologist sentenced to eight years in prison on charges of industrial espionage.

The geologist, Xue Feng, a naturalized American citizen born in China, was convicted in July of violating the country’s vague state secrets laws after he obtained an oil industry database for his employer, IHS Energy, a consulting company in Colorado.

His lawyers say the information was classified as secret only after he bought it. Given the government’s control of domestic petroleum production, several Western industry experts have questioned whether possessing such data could have any impact on China’s security.

The American ambassador, Jon M. Huntsman Jr., who attended the hearing at the Municipal High People’s Court in Beijing on Friday, said he was disappointed by the ruling, which included a fine of about $30,000. “This has been a long, difficult and painful ordeal for Xue Feng, but not only for Xue but also for his wife, Nan, and his two kids,” he said in a statement. “We ask the Chinese government to consider an immediate humanitarian parole of Xue Feng, thereby allowing him to get back to his family and his way of life.”

The prosecution of Mr. Xue has raised troubling questions about the country’s judicial system, which rarely explains its rulings. Mr. Xue told American officials that his interrogators burned him with cigarettes and that he was jailed for five months before being formally charged, a violation of Chinese law.

The case was rife with other irregularities, including restrictions on his access to family and lawyers. During his appeal in December, the American Embassy was barred from the courtroom despite a Chinese-American pact that guarantees defendants consular representation.

In the more than three years since Mr. Xue was detained, American officials have visited him dozens of times, and President Obama raised his case with President Hu Jintao, most recently during Mr. Hu’s visit last month to Washington.

Given the Chinese government’s effective control over the judiciary, human rights advocates said the court’s rejection of the appeal underscores the United States’ limited ability to influence Beijing on matters that would appear to have minimal impact on the country’s rulers.

“There was a period of time when prisoners were part of the calculus of U.S.-China relations, and raising cases at the highest levels would sometimes result in people being released,” said Joshua Rosenzweig, a Hong Kong-based researcher at the Dui Hua Foundation, a group that advocates on behalf of political prisoners. “It’s been a long time since we’ve seen that work.”

Although the motives behind the harsh sentence are nearly impossible to decipher, some analysts have viewed Mr. Xue’s prosecution as a reflection of China’s sensitivity to matters regarding natural resources.

Last year, a Chinese-Australian mining executive, Stern Hu, was sentenced to 10 years, partly on charges of stealing commercial secrets involving China’s iron ore purchases.