The 24-year-old had only just claimed his maiden two-man victory alongside Marko Huebenbecker on Saturday but was at it again a day later as he was joined by Jan Speer, Alexander Roediger and Martin Putze in topping the Swiss podium once again.
The two-time junior world champion led from start to finish as he posted the two fastest runs to claim top spot in two minutes 1.51 seconds.
Compatriot Manuel Machata and his team finished second, 0.21 seconds behind, while Latvian Edgars Maskalans recovered from a disappointing first run to claim bronze.
This was Arndt’s second four-man victory of this World Cup campaign and despite staying second in the overall rankings, he has reduced Alexsandr Zubkov’s lead to just 42 points after the Russian could only manage fourth in St Mortiz.
Meanwhile, the Great British team led by John James Jackson finished 14th in 2:11.56 , while a second time driven by Will Golder finished down in 27th.