Megamonsoon means the strong monsoonal circulation on Pangaea during Permian and Triassic time. Formation of it was closely related with the shape of Pangaea, land-sea distribution and latitudinal distribution onland. As the Pangaea assembled in late Carboniferous epoch and broke in late Jurassic and early Cretaceous epochs, the megamonsoon had undergone the processes of formation, development and decline. During Triassic time, Pangaea was large enough and nearly symmetrical respect to the equator and the megamonsoon attained its maximum strength. The megamonsoon had a such profound influence on Pangaean paleoclimate, paleoenvironment, paleontology and sedimentation that low latitude regions showed an alternative climate of aridity and humid, and evaporites and red beds sedimentation widespread while high latitude regions were warm and humid, and coals wide spread. The Permian and Triassic sedimentary rocks in Colorado Plateau (western U.S.), western Tethys (Europe), and eastern Tethys (China), recorded the features of megamonsoon influence.