The 27-year-old from Glasgow carded 10 birdies, which included holing her third shot at the 14th after a penalty drop from behind a tree, at Golfclub Worthsee.
Her score moved her to 24 under par with an aggregate of 259, one better than Frenchwoman Gwladys Nocera's score at the 2008 Goteborg Masters.
Walker now heads into today's final round with a six-stroke lead over China's Yu Yang Zhang and England's Charley Hull.
A final round of 66 would see her set a new Ladies European Tour record for the lowest 72-hole total, at 30-under-par.
"I feel really comfortable with my game," said the Scot.
"I would love to win and I've just got to try to do the same again and keep playing the way I'm playing."
Hull fired eight birdies for her second 64 of the tournament and is also in contention for her second LET victory this season.
Six birdies and one bogey in a round of 67 ensured 22-year-old Zhang remains in the mix for her first LET trophy.
She said: "I think I will be playing with two long hitters so I will stick to my game plan and just try to make birdies and focus on my shots."
Two strokes further behind at 16-under, French duo Celine Herbin and the 2012 tournament champion Anne-Lise Caudal lie in a tie for fourth spot.