Caroline Graham Hansen and Claudia Pina netted inside the opening 25 minutes before Alexia Putellas added a third on the stroke of half-time.
Graham Hansen and Pina were among six different second-half scorers for the Catalan side, with Mapi Leon, Ewa Pajor, Esmee Brugts and Fridolina Rolfo also among the goals.
England midfielder Keira Walsh featured as a second-half substitute for Barcelona.
Head coach Pere Romeu’s side are looking to make up ground in Group D, having lost 2-0 at Manchester City in their opening game.
Barcelona overtook Hammarby with this victory, while City moved three points clear of both teams, coming from behind to beat St Polten 3-2 in Vienna.
The 9-0 victory for Barcelona matches the club’s record victory in the Champions League, having beaten Portuguese side Benfica by the same scoreline in October 2022.
