The Brazilian won on Easy Touch, Dashing Dart, Mr Stunning, Victor Emperor, Cool And Neat, Beat The Clock, Mighty Maverick and Prawn Baba.
Moreira rode in 10 of the 11 races on the card.
"The feeling I have now is something special," he told the South China Morning Post. "Today has to share the top spot as my best day in racing."
Moreira had eight winners from eight rides at Kranji in Singapore in 2013 and also rode eight in a day in his native Brazil in 2008.
Jockey Joao Moreira has broken a record in Hong Kong by riding eight winners on a single card at Sha Tin.