A Hong Kong man who chanted protest slogans was found guilty of inciting secession on Monday in the second national security case to come to trial as authorities wield a sweeping new law to snuff out dissent.

Ma Chun-man, a 31-year-old food delivery driver, was convicted by a judge of trying to separate Hong Kong from China by chanting slogans and displaying placards, as well as through interviews with reporters last year.

China imposed a national security law in response to massive and often violent democracy protests in the city two years ago, in a move that has brought mainland-style political speech curbs to the once outspoken business hub.

The city's debut national security trial took place in July when a man was convicted of terrorism and secession after he rode his motorbike into police while flying a protest flag.

But Ma's prosecution was more of a legal weather vane because -- much like the vast majority of upcoming national security trials -- his offences did not involve a violent act and centred purely around his speech.

Prosecutors said slogans Ma used that incited secession included "Liberate Hong Kong, revolution of our times", "Hong Kong independence, the only way out", "Hong Kongers, build our own country", "One nation, one Hong Kong" and "All shall be valiant, start armed uprising".

China imposed a national security law in Hong Kong last June, a move that has brought mainland-style political speech curbs to the once outspoken business hub China imposed a national security law in Hong Kong last June, a move that has brought mainland-style political speech curbs to the once outspoken business hub Photo: AFP / ISAAC LAWRENCE

Ma's lawyers said their client was merely trying to prove "exercising freedom of speech is not unlawful". His slogans, they argued, were "empty words" and "a fool's ravings" that did not reflect any plan or resources.

But Stanley Chan, one of the judges specially chosen by the government to try security cases, disagreed and said Ma acted like "a human recorder repeating political statements".

"The defendant was constantly, unreservedly inciting others to commit acts that are explicitly banned in... the national security law," Chan said.

Whether Ma had actual plans or committed acts to separate Hong Kong from China was irrelevant to convicting him of inciting others, Chan said.

"In a society with rule of law, no one enjoys infinite rights and freedom, otherwise the destructive and subversive effects would go without saying," Chan said.

Ma, who has been in detention for the last 10 months, pleaded not guilty and did not take the stand during his trial.

He will be sentenced at a later date and faces up to seven years in jail.