The invention belongs to the field of oil-gas geological exploration, and relates to a sedimentary stratum dividing method. By means of a seismic stratigraphy research method, a seismic reflection coefficient curve is fitted through a logging curve, and accordingly a sedimentary stratum is divided and compared through reflection coefficient features of a deposition interface. The method solves the scientific research situation that area marker beds lack and accordingly strata can not be divided and compared, can overcome the defect that a seismic division vertical sequence resolution ratio is low, and reduces errors caused by manual division and comparison of the strata.