BEIJING — President Xi Jinping of China in effect wrote an epitaph to the shrunken influence of his predecessor and former rivals this week when the Communist Party announced major changes to its once-powerful Youth League, a training ground for many officials who have been marginalized under Mr. Xi.

The Communist Youth League served as a cradle for generations of Chinese leaders, who rose through it into the high ranks of the party. Mr. Xi’s immediate predecessor as China’s top leader, Hu Jintao, was among the most prominent. Others have included Premier Li Keqiang, Vice President Li Yuanchao and Ling Jihua, the former head of the party’s general office.

But a reorganization of the Communist Youth League laid out in the state news media on Tuesday indicated that its glory days as a finishing school for China’s political elite may have passed. The overhaul promised to shrink the Youth League’s central leadership, put it under firmer party control and return it to its grass roots to try to win over the country’s young people.

“Its ranks will undergo shrinkage at the top and replenishment below,” an unnamed Youth League leader said in People’s Daily, the party’s main newspaper, on Wednesday, explaining the reorganization. “In the face of major changes in the social environment and youth population, there are many areas of the Youth League’s development and work that are ill adapted or unsuitable.”