Communists celebrate 90 years in China
Gala performances and celebratory television programmes have been taking place. An epic patriotic film featuring many of China's biggest stars has been released.
A ceremony at the Great Hall of the People in Beijing is being attended by the country's top leaders.
The CPC has more than 80 million members, making it the biggest political party in the world.
Established in July 1921 in Shanghai by a small group of intellectuals, it took power in 1949 after defeating the Nationalist Party in a long civil war.
Under Mao Zedong, China's first communist leader, the CPC began the Great Leap Forward in 1958, a campaign to increase industrial production during which millions starved.
Millions more are estimated to have died during the Cultural Revolution, a crusade launched by Mao in 1966 to purify the CPC.
But after Mao's death in 1976, his successor Deng Xiaoping introduced market reforms which helped turn China into the world's second-largest economy.
The BBC's Michael Bristow in Beijing says hundreds of millions no longer battle poverty, and many are richer than they could ever have hoped.
"History has proved that only the CPC can save China," declared a commentary from the state-run Xinhua news agency on Thursday.
Ultimately, the CPC continues to rule because it does not allow anyone else to, our correspondent adds.
Ahead of Friday's anniversary, propaganda officials oversaw the production of a film on the founding of the CPC, Beginning of the Great Revival.
There have also been a new official history book, and a large number of exhibitions.
The government also launched a new $33bn high-speed rail link, while the country's first aircraft carrier may begin sea trials on Friday.
Our correspondent says many in China support the CPC's rule, and believe that a country with such a huge population and vast lands needs one overwhelming power to govern.