Arndt is hitting form when it matters most in the four-man and headed into the penultimate round, which doubled as the European Championships, with a first and a second from his last two outings.
That put him top of the overall World Cup standings and he made it three top-two finishes in a row in Igls to stay there ahead of the World Championships and the season finale in Sochi.
Defending European champion Arndt topped the rankings after the first run by 0.01seconds ahead of German team-mate Thomas Florschuetz with Switzerland's Beat Hefti a further 0.09 back in third.
And, while Arndt improved his first-run time of 51.70 to 51.63 second time out, Florschuetz and Hefti swapped places with the Swiss pilot taking European silver ahead of the German.
Arndt won by 0.16 ahead of Hefti with Florschuetz 0.02 back on the Swiss pilot for European bronze again while Britain's John Jackson was joint sixth overall and the sixth best on the continent.
He posted the same overall time, 1:43.89minutes, as Manuel Machata for sixth, 0.56 shy of Arndt while British No.2 pilot Lamin Deen and his crew were 19th overall in 1:44.70.
Alexandr Zubkov, who won last time out, saw his bid for the Triple Trophy, awarded to anyone who wins the last three rounds of the season, scuppered as he finished fourth.
Having trailed World Cup leader Arndt by just 14 points ahead of the Igls round, the Russian is now 47 adrift with the last round taking place on the 2014 Olympic track in Sochi next month.