The reigning local champions took an early lead when centreback Gabriel Cividini powered a header into the net.
The visitors suffered a further blow just before halftime when Callum Talbot was shown a straight red card.
Talbot lost possession to Tai Po’s Igor Sartori at the halfway line and pulled him down in a last-ditch effort to stop a counter-attack.
With the man advantage, Tai Po doubled their lead after the break through winger Michel Renner, who smashed the ball into the net after a well-placed assist from James Temelkovski.
Macarthur pulled a goal back in the 70th minute when a Harrison Sawyer header deflected off Temelkovski for an own goal.
But Tai Po managed to hold on for the win and seized the early lead in Group E.
In the other group match, Beijing Guoan and Cong An Hanoi drew 2-2.
