More than 2,200 delegates met to select a new 205-member Central Committee in Beijing's Great Hall of the People.
That committee will meet on Thursday to endorse China's top decision-making body, the Politburo Standing Committee.
The new line-up will be keenly watched for signs of China's future direction amid slowing economic growth and growing pressure for reforms. In a closing statement, President Hu Jintao said the congress had "replaced older leaders with younger ones" and made decisions of "far-reaching historical significance", Xinhua news agency said.
China's leadership change happens every 10 years. The party congress opened on 8 November with a televised work report from Mr Hu, but since then the decision-making has been taking place behind closed doors.While votes are held, key selections are in reality decided in advance by top leaders, with the Politburo Standing Committee line-up to be revealed at on Thursday – 15.11.12.
Xi Jinping and Li Keqiang are expected to become party leader and deputy respectively. Mr Xi is also expected to take over from Hu Jintao as China's president in March 2013. Both were appointed to the Central Committee, as were the leading contenders for inclusion in the Standing Committee.
BBCChinese.com editor Zhuang Chen says the only question now regarding Mr Hu is whether he will follow his predecessor Jiang Zemin's example by retaining the chairmanship of the powerful Central Military Commission. The answer to that will become clear on Thursday.
Across China, meanwhile, recent cases of official corruption have stoked public anger and there have been a series of high-profile mass protests focusing on land grabs and environmental issues.
Mr Hu, in his speech, said the party had to better tackle corruption issues or risk fatal damage, echoing a warning issued 10 years ago. "If we fail to handle this issue well, it could prove fatal to the party, and even cause the collapse of the party and the fall of the state," he said.