In a strong and direct editorial, the state publication China Daily mentions its fear of Taiwan pushing for independence once the bill becomes law, which would then force Beijing to act with force to bring Taiwan under its control.
The Taiwan Travel Act, meant to encourage visits between the United States and Taiwan "at all levels", was passed by unanimous consent on Wednesday, following its approval in the House of Representatives in January.
China expressed anger on Thursday after the US Senate passed a bill promoting closer US ties with Taiwan, but the step drew praise from the self-ruled island which pledged to deepen cooperation.
The legislation allows unrestricted visits by US officials to the island, while Taiwanese officials would be allowed to enter the USA under respectful conditions.
"China is strongly dissatisfied with the bill and resolutely opposes it, and has already lodged stern representations with the USA side", the Chinese Foreign Ministry's spokeswoman Hua Chunying said.
"China is strongly dissatisfied with this and resolutely opposes it, and has already lodged stern representations with the United States side", she told a daily news briefing.
China lodged a diplomatic protest with Washington over passage of the legislation ahead of Trump's likely approval.
White House officials did not immediately respond when asked if Donald Trump planned to sign the legislation.
Another DPP lawmaker, Lo Chih-cheng, warned that China might react in an exaggerated manner to the bill and tensions across the Taiwan Strait could escalate.
The United States has no formal ties with Taiwan but is bound by law to help it defend itself and is the island's main source of arms.
"Which, if she persisted, would lead to the inevitable outcome of triggering the Anti-Secession Law that allows Beijing to use force to prevent the island from seceding", the paper said, referring to a Chinese law passed in 2005.
China's consternation with Taiwan appears to have increased since President Tsai Ing-wen came to power.
Mainland China issued 31 equal treatment measures it wishes to grant Taiwanese people, according to a spokesman from the State Council Taiwan Affairs Office on Wednesday.