The Dalí Museum is about 1.5 hours drive from Barcelona in a small town called Figueres. Although this museum is outside of Barcelona many thousands of tourists visit the Dalí museum each year. You can travel to the museum from Barcelona via train, coach or by driving a car. See below for a map and driving directions from Barcelona to the museum.
For journeys by train to Figueres see the following web page: http://www.renfe.com choose Barcelona as the origin and Figueres as the destination.
For Bus transfers refer to Dalí Museum the following website - you will need the free Adobe Reader to access this page: Timetable for coach transfer between Barcelona and Figueres by Sagales