Ms Pelosi's trip to Taiwan prompted about two weeks of Chinese military exercises near the island. The drills included firing missiles into the Taiwan Strait and sending warplanes and ships across the midline.
The US has said China used Ms Pelosi's visit as a pretext to launch the threatening military drills. Beijing responded by saying the visit undermined a US pledge not to formally recognise the government of Taiwan, which China claims as its territory.
Washington has said Ms Pelosi's trip did not violate that policy.
The trip by the US congressional delegation has drawn more anger from China.
“China will take resolute and strong measures to defend national sovereignty and territorial integrity,” Chinese Foreign Ministry representative Wang Wenbin said at a daily briefing on Monday.
“A handful of US politicians, in collusion with the separatist forces of Taiwan independence, are trying to challenge the one China principle, which is out of their depth and doomed to failure.”
China's Ministry of National Defence earlier said the latest drills were meant to be a “resolute response and solemn deterrent against collusion and provocation between the US and Taiwan”.
Members of the US delegation, led by Ed Markey, a Democratic senator from Massachusetts, met with President Tsai In-wen, Foreign Minister Joseph Wu and Taiwanese legislators, the American Institute in Taiwan said.
After the meeting, Ms Tsai said her administration was working to ensure stability in the Taiwan Strait and maintaining the status quo.
Mr Markey responded by saying Washington and Taipei had a “moral obligation to do everything we can to prevent an unnecessary conflict and Taiwan has demonstrated incredible restraint and discretion during challenging times”.
The delegation was expected to depart Taiwan on Monday evening.
The Associated Press contributed to this report