Xi Jinping met former Taiwanese vice president Vincent Siew on the sidelines of an Asia Pacific Economic Cooperation (APEC) meeting in Beijing.
Xi told Siew that relations should be based on "the common political commitment to upholding the 1992 Consensus and opposing 'Taiwan independence'", China's official Xinhua news agency reported.
Beijing considers Taiwan, which split from the mainland after the 1949 Communist victory in China's civil war and has its own democratic political system, as a rogue province.
China and Taiwan agreed in 1992 that the island and the mainland belong to "one China", allowing for differing definitions of the concept.
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Chinese state-run media recently accused Taiwan of recruiting students to spy on the mainland, a move seen as a reprisal for Taipei's investigation into a former senior official suspected of leaking secrets to Beijing.
Taiwan's President Ma Ying-jeou last month expressed support for continuing pro-democracy protests in Hong Kong, which Beijing has branded as illegal.
Ma called on Beijing to "let some people go democratic first", but mainland authorities brook no suggestion of democratic reforms.
Relations between China and Taiwan have seen gradual improvement under Ma, who has sought greater economic integration while avoiding talk of independence.