When building isochronous stratigraphic framework, offshore oilfields often has few wells, no outcrop and low seismic solution, therefore, the development demands cannot be satisfied. Aiming at this problem, the isochronous slice method is put forward to construct fine stratigraphic framework by fully excavating the seismic data. The isochronous slice method means that the formation is proportionally subdivided when it can’t be recognized by traditional seismic interpretation technology, seismic microfacies of every slice is analyzed, and then upscaled with the geological setting. The finer isochronous framework is built. The method was used in the NmⅡ formation in LD27-2 oilfield for seismic microfacies analysis and fine isochronous framework construction, which is proved reasonable by later production. The isochronous slice method provides a new methodology for not only fluvial reservoir but other complex reservoirs.