1. By RENFE train to the central Barcelona station: Plaça Catalunya. The journey takes 23 minutes. The schedule is the same as that to Barcelona-Sants station. At Plaça Catalunya connect to the local "ferrocarril" train line run by the Catalonian government - the FGC. Take the train that goes to Sabadell and get off at either of the two stations that serve the university: Bellaterra or Universitat Autònima.

2. By RENFE train to the central Barcelona station: Barcelona-Sants. The journey takes 18 minutes. Trains leave every 30 minutes at :12 and :42 minutes past the hour, and they run between 06:13 and 23:15, including weekends and public holidays. At Sants, take the local RENFE train to the station Cerdanyola-Universitat where you can connect with the UAB bus service.
:: http://www.renfe.es

3. By bus (Aerobús) or taxi to Barcelona- Plaça Catalunya. There are airport buses every 15 minutes between 06:00 and 24:00. At weekends and on public holidays, the first bus is at 6:30. Once in Plaça Catalunya, connect to the "Ferrocarril" service as in 1 above.
Telephone +34 93 415 60 20

:: http://www.bcn.es/turisme/english/
     turisme/mobilitat/ser_tra_hom11.htm