Demigration refers to directly applying a specific imaging technique to a migrated section. It is applied primarily to seismic data mapping. In a previous research study,a time-efficient implementation technology of demigration was expounded. In the present study,the Fast Marching Method( FMM) used for traveltime computation in the isochrone-stack demigration,is developed. Furthermore,other key techniques( such as selection of aperture and antialiasing filtering factor) are analyzed in detail. Besides,the detail implementation method and program flow are given,which is shown their good computational efficiency and high-quality demigration effect. This implementation technique is illustrated with both the V( z) model and Marmousi model. It provides a basic method for implementing demigration in the application of seismic data mapping. In a previous research study, a time-efficient implementation technology of demigration was expounded. In the present study, the Fast Marching Method ( FMM) for for traveltime computation in the isochrone-stack demigration, is developed. Further, the other key techniques (such as selection of aperture and antialiasing filtering factor) are analyzed in detail. This implementation technique is illustrated with both the V (z) model and Marmousi model. It provides a basic method for implementing demigration in the application of seismic data mapping.