Barcelona rode their luck before some brilliance from Lionel Messi put them on the verge of reaching the Uefa Champions League final.
Ernesto Valverde's side triumphed 3-0 in the first leg at Camp Nou on Wednesday with Luis Suarez also on target.
Liverpool who had impressed for much of the match now face a tall order to turn the game around, with the second leg at Anfield on May 7.
Suarez had opened the scoring against his former club in the 26th minute as he got on the end of Jordi Alba's cross.
Liverpool had their chances to level with Sadio Mane blazing over from close range, while Mohamed Salah and James Milner both had efforts saved.
Jurgen Klopp's side dominated the second half but could not find a leveller and Messi made them pay for that.
He added the second 15 minutes from time as he netted the rebound after Suarez had hit the bar.
He then put the game even further beyond Liverpool's reach with a curling free-kick eight minutes from time.
Liverpool's night was summed up in the closing minutes as Salah hit the post with the goal gaping after a goalmouth scramble.
Liverpool must now look to bounce back in the Premier League at Newcastle United on Saturday.