Abstract: Mechanic geochemical barriers are the main types of geochemical barriers. There are two forms of mechanic geochemical barriers on the basis of author’s researches. The first mechanic geochemical barrier is formed by change of water-flow velocity, which is distributed in exit of river or depress along piedmont of the Tianshan Mountains. The second one is formed by decrease of air-flow velocity due to resistance of the mountains, which is distributed along margins of the Tianshan Mountains. The studies on element geochemistry and availability show that Ti, V, Mn, Fe, Co, Cu, Zn, Li, K, Ba, B and F are accumulated in mechanic geochemical barriers due to accumulation of clay in soils. The availabilities of B, Cu, Fe are increased with their total contents. The availability of F is affected by the other factors besides its total content, resulting in complex changes in soils. These conclusions have great values for evaluation of environmental quality and planting and fertilizing according to soil types in agriculture.