The world number 25 dropped just 13 points on his serve and saved all three break points he faced in easing to victory in just 59 minutes.
His eighth-seeded opponent, by contrast, produced seven double faults and was no match for Seppi who will now play Malek Jaziri.
The world number 112 beat Czech Lukas Rosol 7-6 (7/5) 6-3 to become the first Tunisian player to reach an ATP World Tour semi-final.
The 28-year-old Jaziri saved all seven break points he faced and converted one of his eight opportunities for victory over Rosol in one hour and 44 minutes.
Croatia's Ivo Karlovic hit 23 aces as he defeated French qualifier Edouard Roger-Vasselin 7-6 (7/4) 6-3 in 83 minutes to reach his first ATP World Tour semi-final since April 2011.
The world number 130 will now meet Thomaz Bellucci after the fourth seed edged a tight match against Jerzy Janowicz 6-4 7-6 (7/3).
Janowicz fired down seven aces, one more than his Brazilian opponent, but it was Bellucci who was more efficient on his serve overall and took greater advantage of his break point opportunities to secure victory in one hour and 46 minutes.
In the women's action, Sofia Arvidsson continued to punch above her weight as she followed up her defeat of number two seed Marion Bartoli with victory over seventh seed Maria Kirilenko.
The Swede produced a superior all-round game for a 6-3 6-3 win and next up for Arvidsson is fellow Scandinavian Caroline Wozniacki, who is currently ranked number 11 in the world and is the third seed here in Russia.
Wozniacki had a tricky 6-2 6-7 (1/7) 6-1 win over fifth seed and defending champion Dominika Cibulkova, serving for the match twice in the second set and getting broken to love each time, before closing out the game in two hours and 11 minutes.
The other semi-final will pit top seed Samantha Stosur against number four seed Ana Ivanovic, after both recorded straight-set wins.
Stosur faced points for a 4-1 second-set deficit before seeing out a 6-1 6-3 win over Klara Zakopalova in one hour and seven minutes.
Former world number one Ivanovic had a mixed service game with five aces accompanied by four double faults but ran out a convincing 6-4 6-1 winner over Serbian Vesna Dolonc.