Liverpool may be top of the group, but the Reds face elimination if they lose to the Austrian champions and Napoli avoid defeat in the other group game against Genk.
The Reds edged Salzburg 4-3 at Anfield in October, meaning the Austrians - who travel Liverpool by three points - can leapfrog them with victory at home.
Liverpool may be eight points clear in the English Premier League race and reigning European champions, but Klopp knows the threat of elimination is very real.
“Tomorrow night is the most important game of our life because there isn’t another one (if we lose),” Klopp said.
“I just expect us to play the best game we could play, but everybody knows it is a final and we are prepared for that.
“Salzburg needs to win against us and we are there. But we are not a typical Champions League winner - we are still ambitious as crazy and will run and fight for our lives and give 100% in every challenge.”
Salzburg boast Champions League top scorer Erling Haaland, while the Reds rested Sadio Mane and Georginio Wijnaldum has recovered from a minor knock.
“We have to show we deserve to go through,” Klopp said.
“If Salzburg go through, they deserve and we won’t. I am not nervous, but I am tense.
“It’s a special situation - if something is important for you, you want to reach it, so it is stress and you learn to live with this stress.
“I lost many important games over my career, but in the last year, it has gone better.”