The meeting, which was agreed on back in October, was arranged in the hopes of resolving their "it's complicated" relationship status, sparked by the July 2016 agreement to install the US' Terminal High Altitude Area Defense system (THAAD) in the South Korean village of Seongju.
China's concerns mainly stem from the possibility of the Land of the Free using the THAAD system to undermine Beijing by using THAAD's radar systems to monitor its military bases and operations.
And though South Korea has promised that the system wouldn't be used to spy on China, suspicions have not been squashed, says Zhang Baohui, director of the Center for Asian Pacific Studies at Lingnan University in Hong Kong.
Speaking to Radio Sputnik, Zhang says the fact that the system is under the control of the US military is what really bothers China.
"The reason [China is upset] is that the THAAD battery in South Korea is being operated by the US military, not by South Korean military," says Zhang. "If the THAAD missile system is bought or purchased by the [South] Koreans or operated by the Koreans then China would not need to worry."
When asked whether or not the US could be preparing for a strike against North Korea, Zhang said the possibility "is low."
"Trump is merely bluffing, he wants to scare the Chinese," Zhang said. "He wants to tell the Chinese that ‘if you don't do more economic sanctions, we'll strike.'"
The US has repeatedly conducted military drills with regional partners Japan and South Korea to put pressure on North Korea following its November 29 missile launch, the first since its September 15 test.
Moon is expected to stay in the Chinese mainland until Friday.