Mr Xi, who visited Ireland in February, is expected to take over from President Hu Jintao, who has stepped aside.
His central role could be good news for Ireland -- Mr Xi enjoyed an official trip here earlier this year during which he held high-level business talks, as well as trying his hand at hurling.
Delegates to a pivotal party congress said that Mr Hu was not re-elected a member of the party's Central Committee today.
Mr Xi was re-elected along with other leading candidates for seats on the party's all-powerful Politburo Standing Committee.
Designated as successor five years ago, Mr Xi will take over as party general secretary from Mr Hu tomorrow and as president next spring, in China's second orderly transfer of power.
Li Keqiang also is due to take over from Wen Jiabao as premier. The new leaders face an economic slowdown and rising unrest among citizens.