Davies (Ducati) set a new qualifying record to claim Superpole at the MotorLand Aragon circuit and was on course to end Rea's winning run after holding off the Kawasaki rider for much of race one.
But the Welshman crashed out on the penultimate lap.
Rea crossed the line ahead of Marco Melandri (Ducati) and team-mate Tom Sykes to maintain his 100 per cent record in 2017.
The Northern Irishman is now 47 points clear of Sykes in his bid for a third successive title.
Read the full article on eurosport.co.uk: Jonathan Rea snatches victory as Chaz Davies crashes out in Aragon