Xi, who is also national president, welcomed Kuomintang (KMT) party head Eric Chu, the official Xinhua news agency reported. Photos showed them smiling and shaking hands at the Great Hall of the People.
The two parties fought a civil war that ended in 1949 with Taiwan splitting from the mainland.
But both sides stress there is a single China, a key concept for Beijing, which is constantly wary of the potential for Taiwan eventually to go its own way and declare independence.
Beijing still regards the island as a province awaiting reunification, and has never ruled out the use of force to achieve it.
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But relations have been improving since Chu's party -- which has a non-confrontational stance towards the mainland -- returned to power in Taipei in 2008.
Xi said Taiwan would receive "priority" on the mainland but did not provide details.
"Our efforts to open up to Taiwan compatriots will be bigger," he said.
"The two sides can consult with each other on (an) equal basis under the principle of One China, and reach a reasonable arrangement," Xi added.
Cross-strait tensions mounted during the 2000-2008 presidency of the Democratic Progressive Party's (DPP) Chen Shui-bian, who espoused pro-independence views anathema to Beijing.
During that period Lien Chan in 2005 made the first trip to the mainland by a KMT head since 1949.
The landmark visit helped pave the way for relations to warm after the KMT's Ma Ying-jeou was elected in 2008. The same year KMT chairman Wu Po-hsiung visited the mainland, the last holder of the post to do so.
Ma was re-elected in 2012 but public sentiment in Taiwan has since turned against cosying up too snugly with Beijing, with voters saying trade deals have been agreed in secret and not benefited ordinary citizens.
In March last year around 200 students occupied Taiwan's parliament for more than three weeks to demonstrate against a controversial services trade pact, while thousands rallied in support of what became known as the "Sunflower Movement".