To make sure the sedimental sources and it’s development of Yanchang Formation is the key of restoring prototype basin , regional tectonic evolution and breakage of western northchina craton in late triassic on southwest edge of Ordos Basin. Taking some sandstone sample of Yanchang Formation from Ruishuihe section as research object, the detrital zircons ages and it's development were analyzed from sandstone samples located in the Southwestern Ordos basin,with the method of LAICPMS,trace element compositions and cathodoluminescence. Combining regional background,tectonic events and paleocurrent survey,the sedimental sources and it's development were comprehensively analyzed, on the basis of the detrital zircons age spectrum and it’s change. The results indicate that the study area was under the regional dextral strike slip dynamic environment in late Triassic. It can be divided into three stages in late Triassic, early stage (231~225Ma)，middle stage(225~218Ma) and late stage (218~210Ma),respectively. In the early stage，there are mainly sediment provenance from Hercynian provenance on north margin of Ordos and Fupin complexes on northwestern margin of Ordos. Meanwhile, some of them and sediment provenance from Qinqi orogenic belts were influxed into SongpanGarze basin through Baojiwudu aulacogen. In the middle stage，there are mainly sedment provenance from Qinqi orogenic belts on southwestern margin of Ordos，Hercynian provenance on north margin of Ordos, Fupin complexes on northwestern margin of Ordos. Meanwhile,Baojiwudu aulacogen began to close. In the late stage，Baojiwudu aulacogen was closed.