Abstract: In order to detailedly characterize the reservoirs in fan deltas and improve the success rate of hydrocarbon exploration, and taking the first and the second members of the Triassic Baikouquan formation on the western slope of the Mahu sag, Junggar basin as examples, the paper proposes a new method for logging-seismic sequence interpretation aiming at discovering the favorable underwater reservoirs in delta fan front. The fine description of the distribution of ancient grooves is carried out for the first and the second members of the Baikouquan formation by using a new method of ancient landform restoration. The logging data and stratigraphic dip are used to judge and characterize the paleocurrent directions. A totally new seismic interpretation model combined with logging-seismic combination technology is applied to find progradation complexes along river flowing directions in ancient grooves. Meanwhile, the favorable underwater reservoirs in the study area are identified by using lake shoreline determination method. The study shows that the fan-delta-front progradation on the slope belt is commonly found, especially in the ancient grooves. Based on the data analysis of seismic inversion, actual core measurement, logging interpretation, NMR, production test and post-drilling evaluation, it has been proved that the new model of progradation complex is reasonable