"I've come out of a small jail and entered a bigger one," Chen Guangcheng says in the secretly shot video, released by a US-based campaign group.
These are the first comments from Mr Chen since his release from prison last September. He accused the authorities of carrying out forced abortions.
China has not confirmed that the activist is under house arrest.
US-based campaign group China Aid says it received the hour-long film from an "anonymous government friend inside China".
In it, Mr Chen's wife filmed what appeared to be a Chinese security agent.
He is perched on a ladder, peering into the house in Shandong province, keeping watch.
'Miserable conditions'Standing in his home, the blind self-taught lawyer then describes how for the past five months he has been under 24-hour surveillance.
His phone has been cut off, and men and vehicles block access to his house. Anyone who tries to help him is threatened, he says.
"I cannot take even half a step out of my house. My wife is not allowed to leave either. Only my mother can go out and buy food to keep us going," said the activist, who used to offer legal advice to local people.
"I can be jailed again at any time, it is very easy. They can say I am a criminal and just lock me up."
Mr Chen said he could be beaten at any time and that any such action would be ignored by the authorities.
"They are trying to provoke me, if I dare to fight back they can accuse me of assault and jail me," he said.
China Aid said it was releasing the video to show the persecution Mr Chen is facing at the hands of the government.
"Mr Chen is living in miserable conditions, cut off from all outside contact, and detained illegally in his home," said Bob Fu, China Aid's founder and president.
"We cannot believe that China is serious about the rule of law when Chen Guangcheng and other rights advocates are jailed, disappeared, or harassed."
Mr Chen has been held ever since he completed a four-year prison term in September.
He had accused local officials of coercing up to 7,000 women in his province into forced abortions or sterilisations.
But he was convicted on charges of damaging property and disrupting the traffic.
Last month US Secretary of State Hillary Clinton highlighted Mr Chen's case, calling for his release together with the jailed Nobel Peace Prize winner Liu Xiaobo and another detained lawyer, Gao Zhisheng.
