The two met on the sidelines of an Association of Southeast Asian Nations (ASEAN) foreign ministers' meeting in Manila, capital of the Philippines, which is the current chair of the 11-member bloc.
During the meeting, the two sides are likely to discuss Chinese President Xi Jinping's expected trip to the US this September.
The meeting comes days after US President Donald Trump accused China of interfering in US elections, a claim dismissed by Beijing and also disputed by many US election security experts.
Trump in May paid a state visit to China, where he also extended an invitation to Xi for a return visit this fall.
Rubio and Wang had held their first face-to-face meeting in the Malaysian capital Kuala Lumpur last year, on the sidelines of an ASEAN summit. The two have held several phone calls while Rubio also accompanied Trump to Beijing during May’s state visit.