Herein, we review available fauna inventory literature regarding Yilan, and updated on the elevational distribution data of snake species recorded in this area since 2003. Thirty-nine snake species, from 8 families were recorded in Yilan. We presumed that the snake species had a continuous distribution between the highest and lowest elevation localities. The relative higher species richness regions occurred at 400-600 and 1,000-1,200 m above sea level. The two snake species composition transformation regions were the contact zone of the Lanyang Plain to the low elevation montane (ca. 200 m in elevation) and subalpine prevalent cloud belt (ca. 1,400 m in elevation) regions.