The Reds were far too strong for the Hong Kong champions, easily accounting for the visitors in front of 3417 fans on Thursday night.
"I think it's credit to the boys because not having much fitness and maintaining that intensity throughout the game," Adelaide coach Airton Andrioli said after his sides' first competitive hit-out in over a month.
"We scored one, then we scored a second and they had to come out and they didn't have the legs to keep up with us, so that's a credit to the players tonight."
United were dealt a blow before kick-off when captain Bart Vriends was injured in the warm-up and replaced by Sotiri Phillis.
Despite the forced change, the Reds dominated from the outset, controlling possession and looking the more likely of the two sides.
Adelaide were rewarded for their endeavour on 19 minutes with stand-in captain Ethan Alagich breaking the deadlock following a well-worked passage of play.
Jonny Yull looped a deft ball over a static Tai Po defence allowing Jay Barnett to run in behind the back four.
Barnett looked up and squared a pass towards the penalty spot where Alagich lashed a left foot half-volley past Ka Wing Tse in the visitors' goal.
The Reds almost doubled their advantage minutes later when Jacob Brazete drove down the left and drove a cross towards the back post.
Barnett was left unchecked but sprayed his effort across the face of goal when it seemed a second goal was certain.
United's second eventually arrived and it only took two minutes following the restart.
Pana Kikianis found himself in acres of space and waltzed forward before threading a delightful through ball between Tai Po's defence for Juan Muniz.
The Spaniard took a touch before settling with just Tse to beat, fired past the goalkeeper and into the net.
Adelaide's impressive performance was capped off by Craig Goodwin who came off the bench and got on the score sheet in the 75th minute. It was another slick passage of play which undid the visitors as Goodwin linked up with Fabian Talladira.
The pair exchanged passes on the edge of the area with Talladira's return ball finding the Socceroo, who controlled with his first touch and buried the shot with his second from 12 metres.
"Congratulations to Adelaide United, they performed better than us," Tai Po coach Lee Chi Kin conceded.
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