Abstract: The central Iran basin is a back-arc marginal sea basin formed in Late Oligocene to Early Miocene with mixed carbonate, evaprites and clastics succession. Based on the integrated study on the sufficient outcrops, wells, loggings and seismic profiles, the sequence stratigraphy framework of Qum Formation was set up. Two second-order sequences (SS1 and SS2) and five third-order sequences (S1-S5) were identified in Qum Formation. This paper analysized sedimentary system evolution and distribution of each sequence period. The results indicted that three times transgression dominated three periods of sedimentary system evolution. They are: sequence S1, the first transgression period (A, B members, C1 sub-member), sequence S2, the subsidence filling period (C2, C3, C4 sub-members), sequences S3-S5, the transgression period again (D-E members). Finally, the authors discussed its signiffcance for oil-gas exploration.