Busquets saw red in the 88th minute of the match for a rash challenge on Benfica captain Maxi Pereira.
The ban will rule him out of Barca's group matches against Celtic, in Barcelona on October 23 and in Glasgow on November 7.
Busquets has three days to appeal the ban.
Meanwhile, Barca defender Eric Abidal is training in the Pyrenees mountains following a liver transplant in April.
The 33-year-old France international had an operation to remove a tumour from his liver in March, 2011, before making a triumphant return two months later to lift the Champions League trophy after Barca's victory over Manchester United in the final in London.