After losing her 100m title on Tuesday, the 18-year-old Lithuanian world record holder swam more than half-a-second faster than anyone else in the one-length preliminaries.
Olympic champion Meilutyte, who had to settle for silver in the 100m, clocked 29.74 for the 50m.
Jamaica’s Alia Atkinson was second quickest with a swim of 30.27. Controversial Russian 100m champion Yuliya Efimova only clocked 30.45 seconds.
Afterwards Meilutyte, who will swim in the semi-finals on Saturday evening, said: “With the 100 being the second day and at the beginning of the meet, everyone was kind of tense, so it was nice just getting out there to race.”
The Plymouth College pupil had said after losing her 100m title to Efimova, who had previously been banned for 16-months for failing a drugs test: “It was a pretty intense final, emotionally and physically, maybe I got too excited and didn’t finish as well as I was expecting, but I’m quite happy with it and it’s a learning experience.”