Bayern will enter as the slight underdogs following a 1-0 defeat in the first leg in Spain, but Alaba believes that home advantage will prove key this evening.
"You saw what our crowd is capable of last year against Barca," he told reporters at a press conference.
"Barca went through hell here and I hope the same happens to Real. We need the fans on our side."
Bayern overcame Barcelona at the same stage of the competition last season, before beating Bundesliga rivals Borussia Dortmund in the final.