Jimenez is a four-time winner this season and also earned a spot on the European Ryder Cup team.
Sergio Garcia, a teammate of Jimenez's on the Ryder Cup squad, posted a 5-under 66 and shares second place with Peter Baker, Peter Hedblom and Marc Farry.
Jimenez got his round going on the back nine on the Alpine Course at Golf Club Crans-sur-Sierre. The Spaniard jumped out of the gate with birdies at the 10th and 11th to open his round.
The 40-year-old parred his next two holes before dropping in his third birdie at the par-5 14th. Jimenez closed out his opening nine with a birdie at the par-4 18th.
Around the turn, Jimenez made it two straight with a birdie at the par-5 first. The 11-time winner on the European Tour moved to 6 under with a birdie at the par-4 fourth. He scrambled to five pars in a row to finish his bogey-free round.
'I am very happy with the things around me at the moment and feel I am hitting the ball very nicely,' said Jimenez. 'I had a good period like this in 1998 and 1999, but feel I now have more experience and am more calm probably.'
Garcia, another Spaniard, got his round going with back-to-back birdies from the second. He drained his third birdie at the par-4 sixth and came right back to birdie No. 7.
However, he tripped to a bogey at the eighth. Garcia slipped back to minus-2 with another bogey at the par-4 12th. He turned it on from there though.
Garcia dropped in a birdie at the par-3 13th and followed with another birdie at the next. He sank a birdie at the 15th to make it three in a row. The four-time winner on the European Tour then parred his final three holes.
'The course was playing tough this afternoon, quite firm although there was no wind,' said Garcia. 'But it was still tough to hit to the pins. On 11, it was almost impossible to get close. The greens were getting firm, but nothing wrong with that. There is nothing wrong with the course playing tougher than years past.'
Hedblom, Farry and Baker each posted six birdies and to go along with one bogey during their rounds.
Luke Donald, a teammate of Jimenez and Garcia on the European Ryder Cup team, shot a 4-under-par 67. He is tied for sixth place with Simon Wakefield, Steven O'Hara, Carlos Rodiles, Martin Maritz, Angel Cabrera and Peter Fowler.
Defending champion Ernie Els bogeyed two of his first four holes, but battled back with five front-nine birdies, to go along with another bogey, to post a 2-under-par 69. He stands in a tie for 24th.