Abstract: One of the key elements of seismic interpretation is the problem of data transformation between time domain and depth domain. And the average velocity is the bridge between time and depth domain. There are two data sources to get average velocity:well data and seismic data.The study area is located in the offshore of Brazil,where the sea-water is deep and the sea bottom varies sharply. Although there are many well data, the distribution of them is uneven. The 3D seismic velocity data is absent, and the filter of average velocity among wells has problems. Base on the tracing of sea bottom, seismic-well tie, and horizons interpretation, the 3D interval velocity model has been rebuilt in Petrel software. And it has been used to provide the precise data in depth domain for reservoir modeling, reserve recalculation, and development well adjustment.