Taiwan is one of the most sensitive of all policy issues for the Communist Party in Beijing, which claims the island as its own and views it as a renegade province, to be bought under its control by force if necessary.
The vote in self-ruled Taiwan is shaping as a contest between two women, deputy parliamentary speaker Hung Hsiu-chu from the Nationalists and the pro-independence opposition Democratic Progressive Party's candidate, Tsai Ing-wen.
On Wednesday, Hung moved a step closer to securing the Nationalists' nomination, after top party officials approved her bid.
In a brief statement carried by the official Xinhua news agency, China's Taiwan Affairs Office spokesman Ma Xiaoguang said he had "noted" the news about Hung, but added, "We do not get involved in, or comment on, the Taiwan election," Reuters reported.
"We welcome any Taiwan party or person as long as they oppose Taiwan independence, recognize the 1992 consensus and promote the peaceful development of cross-strait relations," Ma added.
The "1992 consensus" refers to Beijing's cherished "one China" principle that includes Taiwan as part of China.
Hung advocates a more pro-China policy and has publicly said she would like to sign a peace treaty with China.
China has repeatedly lambasted Tsai in recent weeks, saying she needs to clearly explain her policy towards China and how she intends to keep peace between the two sides.
Nationalist forces fled to Taiwan in 1949 at the end of a civil war with the Communists that has never formally ended, and the status of Taiwan has hung over several generations of Communist leaders without a lasting resolution.