The 25-year-old central midfielder has agreed a three-year deal at the Madejski and completed his medical today (Friday).
The deal will be formally finalised on Sunday, July 1.
Guthrie, a former Liverpool and Manchester United youngster, is Royals second confirmed signing of the season after Garath McCleary, with Pavel Pogrebnyak poised to complete his move to Berkshire soon.
Midfielder Guthrie played almost 100 games during a four-year stint with Newcastle and says it is an 'honour' to join Reading.
"It feels brilliant to have everything agreed, it is a great honour and I am very excited. As soon as I met the manager and Nick Hammond (director of football) my mind was made up, it was a no-brainer," he said.
"Reading Football Club is a fantastic family club, well run and I'm so excited to be part of something special for this club."
Manager Brian McDermott added, "We're delighted Danny is signing for us. He's brings good experience at a good age, he has real ability to pass the ball, he's got energy, he's hungry and is what Reading is all about.
"We're looking to add players who we think will be good for us over a number of years, not just next season, adding to the players who have already done fantastically well for us."