The discovery was made in Shaanxi Province earlier this week.
The tomb, which is 36.5 metres in circumference and 10.1 metres in depth, was badly damaged and only a few burial accessories were excavated, according to Shaanxi Provincial Institute of Archaeology.
From an engraving inside the tomb, archaeologists confirmed the grave belonged to Shangguan Wan'er (664-710), an influential politician and poet during the regime of Empress Wu Zetian (624-705), China's first woman ruler, state-run Xinhua news agency reported today.
"The tiles on the floor had all been ripped up. Perhaps grave robbers came for the treasures and did not have enough time," Yu said.
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Her epitaph has nearly 1,000 words, records the simple message of Shangguan's life, year of death and tomb location, without referring to her literary and political acts.
Shangguan's grandfather and father were prominent officials in the Tang Dynasty but both were put to death because of her grandfather's opposition to Wu's rule.
She was killed in a palace coup in 710. But her legend attracted many Chinese people and remains the theme of many films and TV series now, the report said.
Experts said the findings in the tomb have "major significance" for ancient Chinese literature studies and will provide valuable research data for history and cultural studies of the Tang Dynasty.
The archaeological site of the tomb is closed now, as cleaning and preservation work is still underway but media and visitors across China come to the site every day, it said.
Chinese netizes have tweeted over 470,000 posts about the discovery of the tomb on Weibo, China's microblogging site.
"The inner and outer coffins have not been found, but I heard that there was a small bone piece in the tomb. Does it belong to Shangguan Wan'er?", wrote one microblogger.
"Archaeologists will find out the answer after they conducted scientific research. Perhaps it belongs to Shangguan or an animal," Yu said.