Gao, 69, who was detained in 2024 during a visit from the US, faces a maximum three-year prison sentence, said his wife Zhao Yaliang and Shane Yi, a researcher at the Chinese Human Rights Defenders group which operates outside the country.
The closed-door one-day trial took place at Sanhe City People's Court in Hebei province neighbouring the capital Beijing, and ended without a verdict, Zhao and Yi told Reuters, citing information from his lawyers.
Zhao said she was barred from entering the courtroom.
Verdicts are often announced months later in such trials.
The Sanhe Public Security Bureau did not immediately respond to a request for comment on his case.
The New York-based artist was detained in August 2024 on a family visit to China even though since moving to the United States in 2022, he had made multiple trips to China without issues, Yi added.
"This really shows the Chinese government's logic, when they want to target someone, they can use anything in their power to do so," she said.
"Gao Zhen is an artist. He has a right to artistic freedom, period."
With his brother Gao Qiang, Gao produced several provocative sculptures of Mao that critiqued the 1966-1976 Cultural Revolution, a period of social turmoil and widespread political persecution in China that led to millions of deaths.
European Union diplomats tried to attend the trial but were blocked from entering, its China mission said in an official X post.
Their most famous works include "Miss Mao," featuring Mao with unsettling features like Pinocchio noses and breasts, and "Mao's Guilt" - a bronze statue of the leader kneeling remorsefully.
Gao's wife said she and their seven-year-old son, a US citizen, are under exit bans and cannot leave China.
"This is a huge blow to me," Zhao told Reuters.
"My son hasn't seen his father since the year before last, and we have been barred from sending letters to him since last May. It's had a significant impact on my son's emotions and health."
Gao is suffering from malnutrition and has lumbar spine disease as well as chronic knee and eye conditions that need treatment, Yi said.
Gao was charged for works between 2005 and 2009, Yi said, while China's "Law on the Protection of Heroes and Martyrs" was only established in 2018 and strengthened in 2021.
The law has previously been used to prosecute individuals accused of insulting servicemen and military members who died in the line of duty, as well as historical figures.
A stand-up comedian was censored and his comedy firm fined $US2 million ($A2.9 million) in 2021 after he made a joke that referenced a People's Liberation Army slogan.
