It is the first time a Chinese leader has visited Seoul before Pyongyang, and comes amid cooler China-North Korea ties.
China is North Korea’s biggest trading ally and the nation most able to wield influence over it.
But in recent months Beijing has appeared increasingly frustrated with its unreliable neighbour.
Last year, North Korea carried out its third nuclear test and there are reports that it could be planning a fourth.
Mr Xi and South Korean President Park Geun-hye are also expected to discuss growing economic ties, as the two nations work towards a free-trade agreement.
Wider strategic concerns are also in focus. Both China and South Korea are at odds with Japan over historical issues. But Seoul, like Tokyo, is a major US ally.
South East Asian nations that are, like Japan, involved in territorial disputes with Beijing are also moving closer to the US. So China will be keen to shore up ties with Seoul.
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