Abstract: Judged from grain size probability accumulative curves,grain size parameters and C-M patterns,the Upper Triassic deposits in the Liushan Basin are built up of the fan delta debris flow deposits,subaqueous distributary channel deposits and channel-mouth bar deposits.The Taishanmiao Formation in the lower part displays the evolution from the stronger flow to the weaker flow,while the Taizishan Formation in the upper part is characterized by unstable currents and varying flow velocity.The grain size parameters also indicate that intense turbulent flows may be closely related to the fast velocity of flows and higher contents of suspended particles.