Caledonian movement in Early Paleozoic is an important tectonic event in South China.The corresponding paleogeographic evolution and unconformities play an important role in hydrocarbon accumulation of Lower Paleozoic.Former studies of Caledonian movement focus on South China,and the limited study on corresponding characteristics of contemporaneous tectonic movement in the Upper Yangtze Craton restricted the understanding on its influence to the Lower Paleozoic hydrocarbon accumulation.Based on drilling and seismic data,this study analyzes the contact relationship of Lower Paleozoic,identifies the episodes of Caledonian movement and the development of paleouplifts,discusses the effects of such movements on hydrocarbon accumulation and evaluates the favorable exploration areas in Sichuan Basin.The results show that the extension-dominated Xingkai tectonic cycle ended and the Sichuan Basin entered the Caledonian tectonic cycle dominated by compression during mid-late Early Cambrian.The three episodes of Caledonian movements have obvious responses in Sichuan Basin:the Episode Ⅰ(Yunan movement)during the Late Cambrian developed the Hanzhong-Guangyuan paleouplift in the northwest of Sichuan Basin,the Episode Ⅱ(Duyun movement)during the Late Ordovician formed the central Sichuan paleouplift,the EpisodeⅢ(Guangxi movement)in the Late Silurian led to the final formation of the central Sichuan paleouplift with angular unconformity developing between the Permian and the underlying Sinian-Cambrian.Each episode has undergone a gradual evolution process from quantitative change to qualitative change,which controls the distribution of formations,sedimentary facies and unconformities,and thus determines the pattern of source-reservoir-caprock assemblage and reservoir distribution.The evolution of basin and the formation of paleouplift in the Caledonian period have resulted in the orderly distribution of conventional natural gas in carbonate reservoirs and shale gas resources,and a multi-layered,three-dimensional and big-scale natural gas distribution pattern has been formed around the Caledonian paleouplift.This study has important reference value for guiding hydrocarbon exploration in Sichuan Basin.