This was Kim's fourth visit to North Korea's strongest ally in a year with the first three undertaken in 2018 itself. Tuesday was also reportedly his 35th birthday, though his date of birth has never been confirmed by Pyongyang.
Kim and his wife, Ri Sol-ju, left for China on Monday afternoon for a three-day visit at the invitation of Chinese President Xi Jinping, the state-run Korean Central News Agency reported. He was also accompanied by key diplomats, including Kim Yong Chol, who has overseen negotiations with the US and other foreign countries.
The visit was confirmed by the Chinese Foreign Ministry after a video showed a green train with a yellow strip pulling in to Beijing's railway station on Tuesday morning. Kim was ferried in the same train on earlier occasions.
His visit came amid reports of Kim and Trump gearing up for their second possible meet to discuss the denuclearization of the Korean Peninsula.
Asked if China might use Kim's visit as leverage with the US in its trade talks, Chinese Foreign Ministry spokesperson Lu Kang said Beijing had always been for a solution to the Korean crisis and the visit had nothing to do with a trade war with Washington.
Replying to a question whether Kim's delegation might contact the US trade delegation in Beijing, Lu said the two groups were not on the same level.
China is the North's sole ally and their ties date back to the Korean War in which Mao Zedong's elder son died fighting against the South. It is also believed that the North pays heed to what Beijing says.
Meanwhile, analysts said that Kim's latest trip to China might be intended to demonstrate to the world that their relations remain strong and also reflects the North's push to project its image as a normal state, according to Yonhap news agency.
"It is rare that the North's leader travels overseas at the start of the year. (His trip to China) shows how important it is to advance relations between the North and China," said Yang Moo-jin, professor at the University of North Korean Studies.