The ministry also claimed the summit was organised by the US to "draw lines of ideological prejudice, instrumentalise and weaponise democracy... (and) incite division and confrontation."
Instead, Beijing vowed to "resolutely resist and oppose all kinds of pseudo-democracies".
Ahead of the summit, China ramped up a propaganda blitz criticising US democracy as corrupt and a failure.
Instead, it touted its own version of "whole-process people's democracy" in a white paper released last week that aimed to shore up legitimacy for the ruling Communist Party, which has become increasingly authoritarian under president Xi Jinping.
While the US has repeatedly denied there will be another Cold War with China, tensions between the world's two largest economies have spiralled in recent years over issues including trade and technological competition, human rights, Xinjiang and Taiwan.
The US Treasury on Friday sanctioned two high-level Chinese officials for human rights abuses in the Xinjiang region and placed Chinese AI surveillance firm SenseTime on a blacklist for its facial recognition technology targeting the Uyghur minority.
Taiwan, a democratic self-ruling island that is claimed by China, was invited to the US summit in a clear snub to its larger neighbour.
But Beijing got a boost in the middle of Biden's summit when Nicaragua dropped its previous diplomatic alliance with Taiwan, saying it only recognised China.
The announcement leaves Taiwan with only 14 diplomatic allies. In response, the US State Department called on "all countries that value democratic institutions" to "expand engagement" with the island.