The Wupataerkan Group is characterized by cherts in contact with basalts through a thrust fault in Madaer area, Southwest Tianshan Mountains. However, definite evidence on the age of the group is absent. Based on the radiolarians picked up from the cherts, the authors hold that they were formed in Late Devonian to Early Carboniferous. Eleven chert samples have the SiO2 and Al2O3 content ranging respectively from 88.80% to 93.28% and from 2.02% to 3.72%. Four samples could be classified as pure cherts, which have SiO2 content of 91.0%～99.8%. However, all samples have much lower SiO2/Al2O3 ratios than the pure cherts (80～1400). These values suggest that the cherts contain high ratios of continental margin materials in the sources. The Al/(Al+Fe+Mn) ratios of 0.57～0.72 and Ce/Ce* ratios of 0.90～1.21 suggest that these cherts are genetically biological sediments. Moreover, the Al2O3/（Al2O3+Fe2O3） ratios are between 0.64 and 0.77, 10.92×10-6～26.7×10-6 for V, and 2.15×10-6～34.10×10-6 for Cu. The Ti/V ratios vary from 25.53 to 44.93. The cherts have a total REE concentration of 30.78×10-6～59.26×10-6, averaging 45.46×10-6. The (La/Ce)N ratios range from 0.81 to 1.12, between the typical ocean basin and the continental margin. In 100 Fe2O3/SiO2 versus 100 Al2O3/SiO2, Fe2O3/(100-SiO2) versus Al2O3/(100-SiO2), Fe2O3/TiO2 versus Al2O3/(Al2O3+Fe2O3) and (La/Ce)N versus Al2O3/(Al2O3+Fe2O3) diagrams, the samples fall into the area of continental margin. All these geochemical characteristics suggest that the cherts were formed in a continental margin setting. The Ceanom values range from -0.06 to 0.08. The characteristics of Ceanom＞-0.1 and significant negative Eu anomalies indicate that the sea water was in an anoxic environment during the deposition. In combination with regional geological setting, it could be inferred that the cherts of the Wupataerkan Group were formed in a small ocean basin, probably at the stage of closing of the South Tianshan ocean basin. The researchers have basically reached consistency on the basic process of tectonic evolution history in Southwest Tianshan Mountains. However, there are different opinions about the collision time between Karakum-Tarim plate and Kazakhstan-Junggar plate. The geochemical characteristics of cherts in Madaer show that the cherts got much continental clastic materials during their formation and that their sedimentary environment was a continental margin. The formation age of cherts is from Late Devonian to Early Carboniferous. Based on these results, it is inferred that the ocean basin experienced shrinking in Early Carboniferous. Moreover, the collision time of the two plates is likely to be Late Carboniferous.