Arda Turan, whose two goals against Sevilla helped Barca lift the Spanish Super Cup on Wednesday, gave them an early lead at the Nou Camp before Ruben Castro equalised in the 21st minute.
Barca went back in front thanks to a trademark 37th-minute goal from Messi before Suarez La Liga's top scorer last season, made it 3-1 before halftime.
Messi set up Suarez for the Uruguayan's second in the 56th minute before the Argentine netted again a minute later with a left-foot drive from outside the area.
Suarez then completed his treble with a 25-metre free kick in the 82nd minute.
Betis scored again six minutes from time after Castro struck a right-foot shot beyond goalkeeper Claudio Bravo.
Barca were without several injured players including captain Andres Iniesta and forward Neymar, who is playing for Brazil at the Rio Olympics.
Chile captain Bravo, linked with a move to Manchester City by media reports, started in goal with Marc-Andre ter Stegen out injured.
Barca coach Luis Enrique handed new signings Samuel Umtiti and Lucas Digne their league debuts.
The hosts went in front when Messi's diagonal pass found Jordi Alba and he cut a pass back to Turan who beat Betis keeper Antonio Adan from six metres.
Betis equalised when Bravo got a touch to Castro's powerful free kick but could not prevent the ball going in.
Messi then hit the bar before making amends minutes later when he pounced on Denis Suarez's pass before shooting with venom into the bottom corner of the net.
He carved the Betis defence wide open in the 42nd minute with a pass to Sergio Roberto and he set up Luis Suarez who finished clinically.
Betis, under new coach Gus Poyet, struggled to keep up with Barca in the second half.
Messi and Suarez combined before the Uruguayan beat Adan with an easy tap-in.
The dynamic Messi then found the corner of the net again before Suarez added Barca's sixth goal.
Zinedine Zidane's Real Madrid get their campaign underway on Sunday when they visit Real Sociedad.
(Reporting by Adriana Garcia; Editing by Tony Jimenez)
source: www.abs-cbnnews.com
