Moon is also expected to discuss the North Korean nuclear crisis during his four-day trip, which includes talks with Chinese President Xi Jinping on Thursday.
The US military installed the powerful THAAD (Terminal High Altitude Area Defense) system in the South earlier this year to guard against threats from the nuclear-armed North.
The move angered Beijing, which considers the deployment a threat to its own security.
China slapped a string of measures against South Korean businesses and banned group tours to the South, in moves seen as economic retaliation.
But last month, the two countries issued identically-worded statements on their mutual desire to improve relations.
It did not state any specifics, but Beijing has demanded that Seoul formally promise not to deploy any more THAAD launchers and not to join any regional US missile defence system.
Moon's office said ahead of the trip that the president, who took office in May, wanted to "normalise" ties with Beijing, and that the visit would be a turning point towards a "more mature" relationship.
South Korea's Yonhap news agency said Moon had arrived in Beijing, and would meet with South Korean residents and attend a business roundtable on Wednesday.
Ties recently showed some -- albeit limited -- signs of thaw as China's state tourism board approved last month Seoul-bound group tours from some parts of the country.
"China and the ROK (South Korea) have reached some consensus on dealing with the (THAAD) issue in the current stage," Chinese foreign ministry spokesman Lu Kang said on Tuesday.
"We hope that the issue can continue to be handled properly and that the two sides can bring China-South Korea relations totally back to the track of sound and steady development," Lu added.
China has also urged the United States, Japan and South Korea to suspend joint military drills in the region in return for North Korea to halt its nuclear activities -- an idea consistently rejected by Washington and Seoul.
Beijing has pressed for talks to peacefully resolve the crisis.
Moon's visit comes hours after US Secretary of State Rex Tillerson said Washington was ready to talk to North Korea "without preconditions", though it remains determined to force Pyongyang to give up its nuclear arsenal.
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