Reporters Without Borders said in a statement that the dissident was confined in a two-square-metre bare cell at Nanchong prison after two of its representatives tried to meet him but were turned away by the prison governor.
The dissident's solitary confinement continued for several days after which he was moved to a larger cell with other prisoners.
Huang, who was arrested in June 2000 for publishing political material on his website, is serving a five-year jail term. He was convicted on 9 May.
Huang was arrested after his website, www.6-4tianwang.com, ran foul of the Chinese establishment by posting information on people who had disappeared into police custody.
The site also carried reports on dissident activities, the banned Falungong sect, the separatist movement in Xinjiang and the Tiananmen Square protests.
In the recent past, China has detained several people and put others on trial for dissidence on the Internet.
However, the release last month of Liu Di, another Internet dissident, is seen as a softening of approach by the authorities.
Reporters Without Borders welcomed this move, but said it was not enough. "It should not be allowed to (overshadow) the fact that dozens of Internet users and cyber-dissidents languish in jails in China," it said.
Meanwhile another Chinese dissident, Wang Bingzhang, currently serving a life term in China, is planning a hunger strike to coincide with Chinese's Premier Wen Jiabao's visit to the US.
The Chinese premier will leave on Sunday for a three-day visit to the US.
Wang told his brother Wang Bingwu of the decision on Friday when the latter met him at the Shaoguan prison in Guangdong province, Washington-based Worldrights said on Saturday.
Wang said he planned the strike to protest his "cruel and inhumane solitary confinement at the hands of Chinese prison officials," Worldrights said in a statement.
The two brothers spoke over a telephone across a wall of glass and the moment Wang talked about launching a hunger strike, the line was cut, the statement added.
Authorities then tried to get Wang to change his mind, but the dissident refused.
Wang, a resident of the US since the 1980s, was sentenced to life imprisonment on 10 February after being convicted of espionage and leading a terrorist group.
He was found guilty of providing intelligence to Taiwan between 1982 and 1990 and obtaining "secret military material illegally" in exchange for money.
Friends and rights groups say Wang was kidnapped by Chinese agents from Vietnam where he tried to meet with Chinese labour activists.