Thomas Müller helped Bayern to a one-goal lead at half time, before Mario Gomez, Arjen Robben and another effort from Müller sealed a comprehensive victory for the hosts at the Allianz Arena.
Bayern in charge
Barcelona might have enjoyed more of the possession in the intense opening, yet Bayern looked far more likely to break the deadlock, creating several chances in an entertaining clash between two attack-minded sides.
Robben failed to get the better of the Catalans' goalkeeper Victor Valdes only two minutes into the game, as the Netherlands winger saw himself clean through on goal following Javi Martinez's cheeky back-heeled pass, before both skipper Philipp Lahm and Müller missed further good opportunities for the home side.
Bayern kept up the pressure and their breakthrough finally came in the 25th minute. Dante's header from Robben's cross turned into a perfectly judged cut-back across goal that Müller nodded home for his sixth strike in the current competition. The Bundesliga record champions were extremely compact at this stage, leaving their Spanish opponents little space to operate in.
Tito Vilanova's men did have the odd half-chance in their sixth consecutive Champions League semi-final, however, Dante doing brilliantly in getting a foot to Dani Alves' searching ball for Lionel Messi at the half hour mark and the Barca right-back himself hammering wide just before the interval.
Bayern remained very much in command in the second half, presenting Barca with problems with their remarkable commitment and perseverance. Jupp Heynckes' players kept pushing forward and had their efforts rewarded only three minutes after the restart, when Gomez tapped in Müller's headed pull-back.
By his own standards, Messi was virtually anonymous and Barca's best chance of the evening fell to Marc Bartra, who lashed his shot wide after Xavi's free-kick beat the Bayern offside trap. It came much worse for Barcelona shortly after, though, when Robben crowned a great individual effort to make it three for the Bavarians. Müller then added a fourth late on, flicking David Alaba's low cross into the net to give the Munich side a clear advantage going into next week's return leg at the Camp Nou.
FC Bayern: Neuer - Lahm, Boateng, Dante, Alaba - Martinez, Schweinsteiger - Robben, Müller (Pizarro 83'), Ribery (Shaqiri 89') - Gomez (Gustavo 71')
Barcelona: Valdes, Alves, Piqué, Bartra, Jordi Alba - Xavi, Busquets, Iniesta - Alexis, Messi, Pedro (Villa 83')
Goals: 1-0 Müller (25'), 2-0 Gomez (49'), 3-0 Robben (73'), 4-0 Müller (82')