On Tuesday, Kim and Chinese President Xi Jinping met for about an hour to discuss the looming North Korea-US summit, which is expected to take place this month or next.
Chinese foreign ministry spokesperson Lu Kang, asked during a daily briefing whether there was a connection between Kim's visit and the possibility of another meeting between Kim and Trump, said China believed contact between the United States and North Korea was important.
Shi Yinhong, an worldwide relations professor at Renmin University in Beijing, said Kim's trip would have no direct influence on the progress of trade talks.
North Korean and Chinese state media have announced his visit but provided no details of what he has done since arriving by train on Tuesday morning.
Kim held three summits previous year with Xi, his most important ally, before and after summits with Trump and South Korean President Moon Jae-in.
Kim also said North Korea hopes its "legitimate concerns" would be given due respect, a reference to Pyongyang's desire for security guarantees and a possible peace treaty to formally end the 1950-53 Korean War. The North Korean leader confirmed he remains committed to the consensus reached during the Singapore summit with Donald Trump a year ago.
Xi has yet to visit North Korea since taking office in 2012.
He also credited President Xi Jinping with helping reduce regional tensions, saying "the Korean Peninsula situation has been easing since past year, and China's important role in this process is obvious to all".
Mr Moon, who has over the past year played mediator between North Korea and the United States, said at a news conference on Thursday that Seoul would cooperate with the USA in resolving the issue of sanctions on North Korea.
Kim is accompanied by his wife Ri Sol Ju and leading officials, according to North Korean state news.
Relations between China and North Korea had deteriorated in recent years over Pyongyang's nuclear activities, but Mr Kim has made sure to keep Mr Xi informed about his dealings with the US and South Korea, and ties appear to have warmed.
It quoted Kim as saying North Korea would adhere to its stance of denuclearisation and resolving Korean peninsula issues through dialogue, including a second summit with Trump, in order to achieve results that would be welcomed internationally.
The two sides agreed to make joint efforts to push for continuous new development of China-DPRK relations in the new era, constantly advance the political settlement process of the Korean Peninsula issue, bring more benefits to people of the two countries, and make positive contribution to peace, stability, prosperity and development of the region and the world.
The trip to China came a week after Kim, in his annual New Year's address to the nation, renewed his commitment to denuclearisation but warned that Pyongyang may change its approach to nuclear talks if Washington persists with sanctions.