Abstract: According to our study, the placer-golds in the Altai Moutains is multi-cause of formation, which includes mechanical and chemical cause. The proofs about the chemical cause of formation are：the size of placer-gold is bigger than that of original gold, the percentage of placer-gold is higher than that of original gold；the shape characters of the placcr-gold；the reproduction of gold-placers and the relationship between the sizes of placer-golds and their production time. The evolution history of the Altai Mountains, the condition of hydrologic chemistory and rich precipitation etc. suggested the Altai Mountains ia a region with advantage natural condition for the chemical cause of formation of placer-golds.