The 22-year-old, who also triumphed in the downhill competition on Saturday, edged out his compatriot Matthias Lanzinger by 0.41 seconds in Sunday's race.
With President Vladimir Putin watching on, local prodigy Alexei Bugayev, 16, was faster than Salcher at the top of the slope, but made a mistake and settled for bronze, adding it to the silver he won in the downhill.
From a field of 31 athletes, 12 failed to finish on a tricky course, although there did not appear to be any serious injuries. Three more were nonstarters.
The race used so-called "calculated time," in which each athlete's time is modified by a percentage reflecting the extent of their disability.
Earlier in the day, Slovakia's Jakub Krako took his fourth career Paralympic gold, winning super G in the visually impaired class.
Over the nine days of competition in Sochi, a total of 72 gold medals will be awarded in five sports.