The most senior Chinese official overseeing ties with Taiwan is visiting the island, amid controversy over a proposed trade pact.
China's Taiwan Affairs Office director Zhang Zhijun's visit follows unprecedented protests in Taiwan over the pact in March.
Protesters said the deal would increase Chinese influence and Taiwan's dependence on the mainland.
But Taiwan officials argued that it would benefit Taiwan's economy.
Over the next four days, Mr Zhang is set to meet his counterpart, Taiwan's Mainland Affairs minister Wang Yu-chi, and opposition figure Chen Chu, who is the mayor of the pro-independence city Kaohsiung.
Chinese state news agency Xinhua said he is also expected to engage with ethnic minorities, small and medium-sized enterprises, farmers and fishermen and Taiwanese youth and students.
His visit has already triggered some small-scale protests in Taipei, according to local media, and some groups are warning that there will be more in Kaohsiung.
The trade pact, signed a year ago, has the two countries agreeing to invest more freely in each other's services markets.
It remains stalled in Taiwan's parliament. Lawmakers will discuss it during a session which overlaps with Mr Zhang's visit.
Analysis: Cindy Sui, BBC News, Taipei
The visit comes at a time when China is shifting its strategy on how to build closer ties with Taiwan. It's not a coincidence that Mr Zhang will not be meeting Taiwan's pro-Chinese President Ma Ying-jeou, according to analysts. Beijing wants to de-link itself from Mr Ma, so that opposition to the president and his party and Taiwan's internal politics will not derail agreements and affect China-Taiwan ties.
In addition to trying to present an image through Mr Zhang that Beijing cares about what ordinary Taiwanese people think of how relations should develop, China is also trying to build ties with the opposition Democratic Progressive Party (DPP), so that regardless of which party wins the 2016 presidential race or legislative elections, relations can still progress.
That's why he will meet the DPP's Chen Chu, mayor of Kaohsiung city. Some analysts believe that if the DPP wins, it might actually help Beijing get more economic deals passed because the party will then favour signing trade deals, even if not political negotiations, and there would be little opposition to the deals.
Closer trade could make the island more economically dependent on China, which would ease the way for Beijing to discuss politics with Taiwan.
In March and April, thousands took to the streets to rally against the trade deal in Taiwan's largest-ever protests.
Students stormed Taiwan's parliament and occupied the building for three weeks. By the end of March, more than 60 demonstrators had been arrested and 100 hurt in clashes with police.
China formally regards Taiwan as a part of its territory, despite the island governing itself for six decades. The split came at the end of the Chinese civil war in 1949.
Since then, the Taiwanese have remained sensitive to any signs of China trying to assert its authority over the island.
Earlier this year, however, they held their first direct government-to-government talks. In the past, all talks have gone via quasi-official organisations.
In recent years Taiwan has signed several trade and investment agreements with China, its biggest trading partner.