The hosts strolled into a 4-0 lead in the first half courtesy of a double from Thierry Henry and strikes from Lionel Messi and Samuel Eto’o.
Jean Makoun pulled one back just before half-time and Juninho struck three minutes after the restart.
Things got worse for Lyon as a frustrated Juninho was given his marching orders after picking up a second yellow card in stoppage time and Seydou Keita took full advantage by snatching another in the dying seconds.
After a fairly even opening, a quickfire double from Henry took the match away from Lyon.
After 25 minutes he latched onto a ball over the top from Rafael Marquez, beating the offside trap to slide the ball under Hugo Lloris.
Two minutes later Henry doubled the lead. He was put through by Xavi and slid the ball in at the near post past the advancing Lloris.
The third was all about Messi as he showed his class in the 40th minute.
The Argentina star collected the ball on the right touchline, before embarking on a mazy run past three Lyon defenders.
He then exchanged a one-two with Eto’o, before firing a low shot home.
By this point Eto’o was desperate to get on the scoresheet himself as he stormed into the box from the left, only to see his shot saved by Lloris from point-blank range.
Within a minute, though, he had made amends as he popped up in the box, side-stepped his marker and smashed the ball home.
Barca were thoroughly dominant but Lyon managed to make some home hearts flutter as they mounted a comeback either side of half-time.
A minute from the break, Makoun made it 4-1 as he headed home Juninho’s corner.
And the former Brazil midfielder got on the scoresheet himself three minutes after the break following a cross from Cesar Delgado.
Any thoughts of a comeback soon crumbled though, as Barca continued to create a raft of chances, Henry having a low shot saved by the keeper when through one on one, while Messi could have bagged himself a hat-trick. At the other end Karim Benzema fired a left-foot shot over the bar from 12 yards.
As the game moved, into stoppage time, Juninho picked up a second booking for dissent and moments later Keita made it five for Barca.
The Mali midfielder was played through by Xavi and took the ball past the out-rushing Lloris before dispatching the ball into the back of the net.
BARCELONA: Valdes, Dani Alves, Marquez, Pique, Sylvinho, Xavi, Toure Yaya, Iniesta (Hleb 90), Messi, Eto’o (Bojan 87), Henry (Keita 75).
LYON: Lloris, Clerc (Bodmer 46), Cris, Boumsong, Grosso, Delgado (Kallstrom 61), Juninho, Toulalan, Makoun, Ederson (Keita 85), Benzema.
Referee: Tom Henning Øvrebø (Norway).