Former Arsenal midfielder believes Liverpool will win comfortably.
The Reds drew their opening game in the competition away to Bordeaux, and a victory over the Swiss side would leave them in a comfortable position to qualify for the knock out stages.
Liverpool struggled at Anfield in the Champions League last season, and will need to get the crowd onside early to work in their favour.
Merson told SkySports that Liverpool will win the game with ease.
He said: "I expect them to win this game, even though they've got a massive match on Sunday against Everton, I expect them to win this 3-0."
Brendan Rodgers' team selection is likely to be impacted by the weekend's Merseyside Derby, but Liverpool need all the momentum they can get right now to take to the clash at Goodison Park.
Sion themselves are in a poor moment, having lost their last two games 2-0 and 1-0, including a home defeat to Liechtenstein based FC Vaduz, who play in the Swiss league.
Failure to get the three points would be even worse in that context, and place the Reds under even more pressure heading into the weekend's clash.