Syndepositional deformation structures were well developed in the lacustrine delta front deposits of Chang 4+5 oilbearing intervals of the Upper Triassic Yanchang Formation in the Ordos Basin. It is concluded that these structures， such as sand balls，sand pillows，ballpillows， graded microfaults， microfissures， liquefied convolute deformation beddings were mainly produced by seismic liquefaction. According to seismite sedimentary characteristics，seismic sedimentary process can be divided into A， B， C， D and  E  units， which are respectively associated into five sedimentary sequence types，namely as type ABCD， BCD or CD， AB，BCE or BE and BEBE， of which types BCD(CD)and AB are the most dominant types. Through analyses of the palaeotectonics， it indicates that the paleoseismic activities are mainly formed due to the activation of the northwesttrending basement and the activities of the northwesttrending and northeasttrending growth normal faults in the depression center during the Late Triassic in the Ordos Basin.