The Baggies host the Reds in the third round of the league cup and Lukaku, on loan from Chelsea, is of the belief that Brendan Rodgers' side will be determined to avenge the 3-0 Premier League defeat at The Hawthorns on opening weekend.
"To beat them in the league was a big achievement for us but we know Liverpool will want revenge," Lukaku told The Independent.
"We have to be ready. It's going well for us now and we just have to keep both our feet on the ground.
"If we want to keep our momentum going, we want to win this game and it would also mean we could go with a clear mind to the derby at Aston Villa [on Sunday]."