Freedom on the Net 2018 report found online propaganda and disinformation have increasingly "poisoned" the digital space, while the unbridled collection of personal data is infringing on privacy.
"Democracies are struggling in the digital age, while China is exporting its model of censorship and surveillance to control information both inside and outside its borders," said Michael Abramowitz, president of Freedom House.
"This pattern poses a threat to the open internet and endangers prospects for greater democracy worldwide."
Chinese officials have held sessions on controlling information with 36 of the 65 countries assessed, and provided telecom and surveillance equipment to a number of foreign governments, Freedom House said.
The accusations made by Freedom House are "without basis, unprofessional, irresponsible, and have ulterior motives," said Chinese foreign ministry official spokesman Lu Kang at a regular press briefing in Beijing on Thursday.