The trio are being held in custody.
The arrests were made under the National Security Act passed in 2023, which is intended to allow prosecutors to put spying suspects on trial in a wider set of circumstances.
Searches were carried out at the properties where the three men were arrested as well as other addresses in London, Wales and Scotland, police said.
"While these are serious matters, we do not believe there to be any imminent or direct threat to the public relating to this," the head of counter-terrorism policing in London, commander Helen Flanagan said in a statement.
Security minister Dan Jarvis said there would be "severe consequences" if it is proven that Chinese authorities attempted to interfere with the sovereign affairs of the United Kingdom.
"The National Security Act provides our intelligence agencies and law enforcement with the modern legal tools they need to deter, detect and disrupt the full range of state threats," he told MPs.
"The action counter-terrorism police have been able to take this morning is an example that that legislation is working well."
with PA
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