While addressing the ceremony, Xi, also the general secretary of the CPC Central Committee, appreciated the support from Russian President Vladimir Putin and other Russian leaders for the project.
Eighty five years ago, for the future of China and the Chinese nation, more than 140 CPC delegates from all parts of China risked their lives and came to Moscow to hold the Party congress with the help of the Russian people and some international organizations, Xi said.
That meeting has played a key role in Party building and its development, as well as in the cause of the liberation of Chinese people and China's revolution, he said, adding that it is the only Party congress held overseas in the CPC's history.
The Chinese president said the site of the congress is an important symbol of the profound friendship between the peoples of the two countries.
The CPC, the Chinese government and the Chinese people highly value that particular period of history, and also treasure the history of mutual support between the two peoples, he added.
The establishment of the memorial is to remember the history, carry forward the traditional China-Russia friendship, and promote the two nations' friendship for the future generations, he added.
Russian Deputy Prime Minister Olga Golodets, who also attended the ceremony, said that the project has reflected the mutual understanding between the Russians and the Chinese, and their friendship, adding that he believed it would become another symbol of bilateral friendship.
Back in 1928, during a time of "white terror" in China, then CPC central committee decided to convene the 6th Party congress in Moscow.
During his visit to Russia three years ago, Xi, who was Chinese vice president at that time, proposed to build the memorial while meeting with then Russian Prime Minister Putin, who strongly supported the idea.