The letter spoke of detention and torture at the hands of the Chinese authorities.
About 1,000 members from around the world heard harrowing allegations of persecution on mainland China and called on President Jiang Zemin to halt the crackdown.
They were meeting in Hong Kong's city hall, taking advantage of the former colony's autonomy to defy the ban on the movement in the rest of China.
Practitioners say China has tortured 120 followers to death while in custody. Chinese authorities have acknowledged several deaths in custody but say most were suicides or the result of illness.
A personal account of ill-treatment was given to the conference in the form of a letter, because the member - whose name and identity were kept secret - was unable to travel to Hong Kong.
The letter spoke of detention and torture at the hands of the Chinese authorities.
While the movement is legal in Hong Kong, the organisers have complained that a dozen people trying to attend the conference were detained by immigration officers at the airport.
Some, they said, were holders of Chinese passports and one was an Australian citizen who had come to talk about her experiences of being jailed in Beijing.
The group said it believed the detentions were made because of pressure from the central government. Hong Kong's immigration authorities refused to discuss individual cases.
'Evil cult'
The Chinese authorities say behind Falun Gong's appearance as a meditation movement it is really an evil cult harmful to those who join.
The Beijing Daily has launched a fresh editorial attack, accusing Falun Gong of teaming up with unidentified "anti-China" forces abroad to sow discord and destabilise the country.
Government statements have expressed alarm over a message by the movement's exiled leader, Li Hongzhi, appearing to say that followers are justified in resisting state suppression of it.
"Li Hongzhi's claim that he doesn't take part in politics and doesn't oppose the government is a cheap lie," a Beijing Daily editorial said.
Wreaths and placards
On Saturday, around 800 Falun Gong adherents performed exercises in a public park in Hong Kong, forming their bodies into the Chinese characters for "truthfulness", "benevolence" and "tolerance".
Others stood in the city centre carrying placards with the names of the 22 countries they represented.
The movement, loosely based on Taoist and Buddhist doctrine, teaches meditation and exercise. It is also known as Falun Dafa.