Sri Lanka won the toss and put England in to bat before right-hander Claire Taylor top-scored with 70 in her team's total of 160-5 off 20 overs.
Danielle Hazell was the pick of the English bowlers with 3-9 from 2.3 overs as Sri Lanka were all out for just 81. England begin the defence of their ICC Twenty20 trophy on Wednesday against Australia at Warner Park, St Kitts.
"I'm really pleased how the two warm-up games have gone, everyone has had a run out," reflected captain Charlotte Edwards, whose side beat India by 25 runs in their first warm-up on Sunday.
"The girls are ready and raring to go now for Wednesday. It's always great to play the Aussies. "We had the best of them in the last World Cup.
But I'm sure they are going to come hard at us on Wednesday, its going to be a fantastic game." England's other Group A opponents are South Africa and hosts West Indies. New Zealand, India, Sri Lanka and Pakistan make up Group B.