Another former chairman of the group and also a former chairman of the city’s largest opposition Democratic Party, Albert Ho, 74, pleaded guilty in January.
He was sentenced to five years and two months in jail.
The Hong Kong Alliance, which had repeatedly called for the “end of one-party dictatorship”, faces a fine of HK$1.5 million (US$191,304), the court judgment said.
Lawyers for Lee and Ho were not immediately available for comment. Chow, a Cambridge-educated human rights barrister, represented herself.
Li Kwai Wah, chief superintendent of Hong Kong’s National Security police, said the trial was “fair, impartial, open and transparent”.
China’s National Security Office in Hong Kong said the defendants “long incited public hatred, hatred, and defection toward the state in various ways”, it said in a statement.
It added that the activists incited the public “to overthrow the leadership of the Communist Party of China and undermine the fundamental system of the country”.
Prosecutors had argued the primacy of the Communist Party was enshrined in Article 1 of the Chinese constitution. Defence submissions that the defendants genuinely believed they were acting within the law given Hong Kong’s freedoms of speech were rejected by the judges.
“Like many people, I feel they shouldn’t have been in jail for one day. It is a very sad day for Hong Kong,” said Hong Kong pro-democracy politician Emily Lau.
Since taking effect in 2020, Beijing’s national security law is part of a wider legal crackdown that has quieted dissent in the China-ruled city, long considered one of the freest in Asia.
China says the national security law restored order “from chaos” after the months-long protests and provides the stability required for Hong Kong’s future economic prosperity.
