The Cameroonian international was one of Arsene Wenger's best players last season, and the Gunners boss is thought to be very keen to hold on to the midfielder.
But Barca look ready to test the north London club's resolve with a £12m bid for the holding midfielder. The La Liga giants let Seydou Keita leave the club earlier this summer, and the Catalan side are keen to bring in a replacement before the season starts on August 18.
Barca have only turned to Song after their first-choice target, Athletic Bilbao and Spain star Javi Martinez was priced out of a move. Bilbao will reportedly not accept less than the value of Martinez's release clause, believed to be around the £30m mark.
And the Spanish side believe they can get an equally talented midfielder for half the price, hence their interest in Song.
The Arsenal star chalked up 11 league assists last season, despite playing a deep lying holding role, and Barca have identified Song's passing as one of his top attributes, fitting in perfectly with their tiki-taka philosophy.
Song's Arsenal contract expires in 2014, and with the future of Robin van Persie and Theo Walcott still uncertain, Arsene Wenger will be eager to ensure that Song's future doesn't become the subject of another summer-long transfer saga.