Kusal Perera notched his third ton as Sri Lanka posted 377-8 from their allotted 50 overs after Ireland captain William Porterfield won the toss and elected to field in the second one-day international at Malahide on Saturday.
Seekkuge Prasanna smashed 95 off just 46 deliveries while Dhanushka Gunathilaka scored 63 runs.
Tim Murtagh was the pick of the bowlers for the home side with figures of 3-66.
Sri Lanka made two changes to the team which won the first encounter of the two-match series by 76 runs under the Duckworth/Lewis method on Thursday, when they were also sent into bat by Porterfield.
Suranga Lakmal, a pace bowler, and experienced allrounder Farveez Maharoof, who took four wickets in a 2007 World Cup finals match against Ireland in Grenada, came in for Nuwan Pradeep and Dhananjaya de Silva.
Ireland make one change, with offspinner Andy McBrine in for fast-medium bowler Max Sorensen.
