Alexia Putellas was involved in two goals in a match where Bayern's Magdalena Eriksson remained on the bench throughout the match.
Barcelona lost last year's final to Arsenal and now face Lyon, who lost the final two years ago.
Lyon knocked out Arsenal in the semi-final. The French giants have won the Champions League eight times, the most of any club. Barcelona has three titles.
The final will be played at Ullevål in Oslo on May 23.
