The figure compared with an investment gain of HK$23.5 billion in the year-ago period, and a revised HK$121.6 billion investment income in the second quarter in 2020.
For the January-September period, the investment income amounted to HK$62.4 billion, compared with HK$201.9 billion a year earlier.
The fund saw gains on bonds of HK$83.2 billion in the first nine months, however, both Hong Kong equities and foreign exchange recorded losses of HK$19.9 billion and HK$9.7 billion, respectively.
"Hong Kong's financial market and the Linked Exchange Rate System (LERS) continue to operate effectively," HKMA Chief Executive Eddie Yue said during a presentation at the Legislative Council of Hong Kong, reiterated that the LERS does not need to change.
Yue said the outlook for the fourth quarter is "very uncertain" and "very hard" to foresee, due to Brexit negotiation and COVID-19 pandemic, which will drag down global economy in the short term, while the long-term impact can't be ignored.
Commenting on the upcoming U.S. presidential election, Yue said the outcome might be contested and cause market panic, but he was confident that Hong Kong's robust financial system is well positioned to withstand such shocks.
The territory's de facto central bank said it will continue to be defensive and put liquidity as one of the most foremost factors in consideration to preserve capital, but urged the public to manage risks.
The HKMA is the key manager of the Exchange Fund, which is under the control of the financial secretary and invests in equities, bonds, foreign exchange and other securities and assets.
($1 = 7.7543 Hong Kong dollars)
(Reporting by Twinnie Siu and Donny Kwok; Editing by Shri Navaratnam and Rashmi Aich)