Ronaldo opened the marking 2 minutes before half-time with a deflected effort off Matteo Darmian.
Andreas Cornelius’ powerful header restored parity, however Ronaldo slotted home Paulo Dybala’s pass to revive Juve’s lead 3 minutes later.
The result lifts Juventus four points afar from second-placed inter Milan.
Ronaldo is the first player to score in seven consecutive league games for Juventus since David Trezeguet netted in 9 sequential matches in 2005.
The Portuguese forward went close to finishing his hat-trick within the last half, shooting straight at Parma goalkeeper Luigi Sepe from a decent angle.
Juventus keeper Wojciech Szczesny had to be on his toes to deny Jasmin Kurtic and Hernani as the guests pushed for a late equaliser, whereas Matthijs de Ligt did well to dam Mattia Sprocati’s goal-bound effort late on.
Inter Milan did not place pressure on Maurizio Sarri’s side earlier within the day, drawing 1-1 with struggling Lecce.