On this page you will find your transport options for traveling between Barcelona and Santander.
Barcelona to Santander by BusThe bus from Barcelona to Santander takes about nine hours and costs about 50 euros. You can book the bus here: Book Bus from Barcelona to Santander.
Barcelona to Santander by TrainThere are no direct trains from Barcelona to Santander. You would have to change in Madrid.
An alternative would be to take the train to Bilbao and then the FEVE narrow-gauge railway from Bilbao to Santander. This must be booked in person and rail passes are not valid. Also, the bus would still be quicker.
Book Train Tickets in Spain (book direct).