The Spain international has stressed that there are no favourites at this stage of the tournament and says it will be important to have Cristiano Ronaldo fit
Pep Guardiola's side head into the clash having been odds-on to defend their Champions League crown throughout the tournament, but Alonso is confident his side have what it takes to avenge their last-four defeat in 2012 to the German champions.
"We haven't thought about what happened two years ago because the circumstances were different. We have to play a perfect match. We have to know how to defend and to attack well when we have the ball," he told a press conference.
"Bayern are a great rival but we are going through a good moment and nobody is the favourite. We've made it into the semi-finals in each of the last three years and now we want to take the next step."
Cristiano Ronaldo returned to training at the start of this week after recovering from a hamstring problem and Alonso is hopeful the Portugal star will be ready to play.
"Ronaldo will play if he is 100 per cent fit. The coach, the staff and the player himself will decide. He is important for us," he said.
"Ronaldo can create and score goals. We use him whenever he is available."
Alonso also praised the performances of Gareth Bale during his first season with the club, stressing that the squad had been thrilled with his efforts even before his stunning winning goal against Barcelona in the Copa del Rey final.
"Irrespective of the goal, Gareth Bale has been very valuable for us and we're very happy with him, especially since it is his first season," said Alonso.