The Airport Authority says the number of passengers using the airport in August dropped 12.4 percent to six million, when compared to same month last year. Last month, anti-extradition protesters held demonstrations at the airport and paralysed traffic nearby. This led to some flights being suspended.
The authority said passenger traffic to and from the mainland, and south-east Asia, both experienced sharp declines.
Cargo through-put dropped 11.5 percent year-on-year to 382,000 tonnes in August on the back of slowing global trade.
Over the first eight months of this year, the airport handled 50.6 million passengers, up 0.3 percent compared to the same period last year.
Cargo through-put though fell 7.4 percent.