Unbeaten Les Bleus have dispatched Italy and Scotland so far this championship, keeping them on course for a Grand Slam decider against Wales on March 17.
But Dusautoir insisted the intensity of their campaign will increase with Ireland's arrival at the Stade de France for a rescheduled match initially postponed due to a frozen pitch.
"This is our first real test when you see the level of Ireland at the moment," he said.
"You run on to the pitch knowing you are going to play a really good team.
"We have had to prepare for this match twice and we have been able to witness their approaches to the ruck and tackling.
"These areas will demand a lot of us. We must be ultra-determined.
"With England and Wales to come, the fixture list in this year's tournament shows that each match requires us to up our level of play.
"However, all I'm thinking of is tomorrow as we have enough on our plates there to occupy our minds and our bodies."
Dusautoir accepts France can ill-afford to repeat the poor starts they made against Italy and Scotland if they are to overcome Ireland.
"We all realise we haven't started the two matches well, but I would rather be in the dressing room after the game celebrating a victory with my team-mates, however we started the game," the Toulouse openside said.
"But seriously, we have to start in better fashion. We have to focus more on this area.
"The way we reacted to that slow start in Scotland shows that we are taking it seriously. We have taken things in hand."
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