The planned auction of the original model for the painting of Mao Zedong that hung above Tiananmen Square has sparked fierce opposition on the web.
Some are calling for the portrait to be sold to a Chinese museum
Thousands have been using Chinese internet chat rooms to express their dismay at the sale due next month.
The painting, by Mao portrait artist Zhang Zhenshi, is expected to fetch one million yuan ($120,000, £66,000).
There were reportedly more than 18,000 posts opposing the sale on one Chinese internet portal alone, sina.com.
"I strongly oppose the auction of Chairman Mao's portrait because it is neither a mere piece of artistic work nor a commercial activity," one anonymous person wrote.
"Mao Zedong is the spirit of our great nation."
Another wrote: "How dare they do such a thing! If they sold Mao's portrait today, they will sell Tiananmen Rostrum the other day."
Zhang Zhenshi, known for his portraits of Mao, was one of more than 30 Chinese painters invited to paint the leader to mark the first anniversary of the People's Republic of China in 1950.
It was the model for the painting that hung above Tiananmen Square, the symbolic heart of China's communist revolution, during the 1950s.
A portrait of Mao Zedong still hangs in Tiananmen Square
Mao is still revered as the father of modern China, despite spearheading radical changes that led to a decade of turmoil and the deaths of many Chinese.
Some people are calling for the portrait to go to a national museum.
"The portrait is worth far more than its monetary value in terms of art and history," Chen Lusheng, a researcher from the China National Museum of Fine Arts, has been quoted as saying.
The painting, owned by a Chinese-American, is due to go under the hammer on 3 June.
The Beijing Huachen Auction Company says the sale will be open to both Chinese and foreign bidders.
But the auction comes at a sensitive time - a day before the anniversary of the 1989 military crackdown on pro-democracy students in Tiananmen Square.
This year is also the 40th anniversary of the cultural revolution, when Mao urged students and workers to form squads of radical Red Guards and rebel against teachers and intellectuals.